IC-NRLF 


THE  LIBRARY 

OF 

THE  UNIVERSITY 
OF  CALIFORNIA 


PRESENTED  BY 

PROF.  CHARLES  A.  KOFOID  AND 
MRS.  PRUDENCE  W.  KOFOID 


RSATIONS 


THE  AJTIMAL  ECONOMY: 


DESIGNED  Ff  R  THE 


INSTRUCTION  OF  YOUTH 


AND 


^ERTTff  Ati  OF  CUSNEHAXi  BTS  A 


BY  ISAAC  RAY,  M.  D. 


,  ,  I  esteem  myself  as  composing  a  solemn  bymn  to 
the  great  Architect  of  our  bodily  frame,  in  which,  I  think,  there  is  more  true  piety, 
tban  in  sacrificing  hecatombs  of  oxen,  or  in  burning  the  most  costly  perfumes. 


PORTLAND: 


PUBLISHED  BT  SHIRLEY  AND  BTDK. 


1829. 


DISTRICT  OF  MAINE,  TO  WIT  : 

DISTRICT  CLERK'S  OFFICE. 

IRIS  IT  "REIYIISIYIBEHESD.  Tnat  on  t06  eleventh  day  of  May,  A.  D. 

JD  1829,  and  in  the  fifty-third  year  of  the  independence  of  the  United  States  of 
America,  Messrs.  Shirley  &  Hyde,  of  said  Dist-ict,  have  deposited  in  this  office 
the  title  of  a  book,  the  right  whereof  they  claim  as  proprietors,  in  the  words  fol- 
lowing, to  wit : 

Conversations  on  the  Animal  Economy,  designed  for  the  instruction  of  Youth, 
and  the  perusal  of  general  readers.  By  Isaac  Ray,  M.  D — In  explaining  these 
things,  I  esteem  myself  as  composing  a  solemn  hymn  to  the  great  Architect  of 
our  bodily  frame,  in  which,  I  think,  there  is  more  true  piety,  than  in  sacrificing 
hecatombs  of  oxen,  or  in  burning  the  most  costly  perfumes. —  Galen.  Portland, 
published  by  Shirley  <fe  Hyde,  1829. 

In  conformity  to  the  act  of  the  Congress  of  the  United  States,  entitled  "  An 
Act  for  the  encouragement  of  learning,  by  securing  the  copies  of  maps,  charts, 
and  books,  to  the  authors  and  proprietors  of  such  copies,  during  the  times  there- 
in mentioned-,"  and  also  to  an  act,  entitled  "  An  Act  supplementary  to  An  Act 
entitled  An  Act  for  the  encouragement  of  learning,  by  securing  the  copies  of  maps, 
charts  and  books,  t«  the  authors  and  proprietors  of  such  copies,  during  the  times 
therein  mentioned ;  and  for  extending  the  benefits  thereof  to  the  arts  of  designing-, 
engraving,  and  etching  historical  and  other  prints." 

J.  MUSSEY.  Clerk  of  the  District  of  Maine. 

A  true  e«py  as  of  record, 

Attest,  J.  MUSSEY,  Clerk  D.  C.  of  Maine 


GIFT 


QP37 


TO 

PARKER  CLEAVELAND, 

Professor  of  Mathematics  and  Natural   Philosophy,  and 
Lecturer  on  Chemistry    and   Mineralogy, 

IN  BOWDOIN  COU.SCUS, 

This  humble  attempt  to  aid  the  cause  of  education,  and 

The  diffusion  of  useful  knowledge, 

Is  respectfully  inscribed, 

As  a  tribute  of 
GRATITUDE  AND  ESTEEM. 


158 


ADVERTISEMENT. 

The  increasing  taste  for  the  study  of  the 
Natural  Sciences,  has  created  the  necessity 
of  an  elementary  work  on  the  most  interest- 
ing of  them  all,  the  science  of  the  Animal 
Economy,  in  which  every  thing  of  a  strictly 
professional  nature,  and  whatever  else  would 
be  improper  for  general  readers,  should  be 
carefully  excluded,  and  the  whole  rendered 
intelligible  to  the  minds  of  the  young  and 
the  unlearned.  To  meet  this  necessity  has 
been  the  object  of  the  author  in  preparing 
the  following  sheets.  To  the  merit  of  origin- 
ality, he  lays  no  pretensions  ;  but  if  the  man- 
ner in  which  the  subject  is  here  treated, 
shall  prove  an  inducement  to  acquire  some 
useful  and  interesting  knowledge  concerning 
the  noblest  of  the  works  of  nature,  it  is  the 
only  merit  that  he  would  claim.  How  far  he 
has  succeeded  in  accomplishing  this  object,  is 
for  instructers  and  common  readers  to  say. 

Portland,  May  11,  1829. 
1* 


CONTENTS. 


CONVERSATION  I. 

Anatomy — comparative  Anatomy — Physiology — Life — distinc- 
tions between  organic  and  inorganic  bodies —between  animal 
and  vegetable  beings — the  primitive  Tissues,  cellular,  muscu- 
lar, nervous— properties  of  the  cellular  Tissue— of  the  muscu- 
lar— elementary  composition  of  the  Tissues 13 

CONVERSATION  II. 

Digestion — possessed  by  vegetables  as  well  as  animals — alimen- 
tary canal — its  coats — the  teeth — mastication — lateral  motion 
of  the  jaws — deglutition — descent  of  the  food  into  the  stom- 
ach— abdomen — the  stomach 34 

CONVERSATION  III. 

(Shymificatioii— the  gastric  juice — artificial  digestion — digestion 
in  Birds— digestion  of  liquids— influence  of  digestion  upon 
the  other  functions  of  the  body — effect  of  exercise  upon  diges- 
tion—influence of  the  mind  upon  digestion — drinks — natural 
diet — chylification — bile — liver — pancreas — spleen— -lacteals — 
rumination — digestion  of  reptiles  and  fishes— of  Mollusca  and 
Zoophytes ,...., 48 

CONVERSATION  IV. 

Circulation— the  blood— connection  of  the  circulation  with  res- 
piration—blood vessels — the  heart — arteries— veins — blue 
boys- -motion  of  the  heart — anastomosis  of  arteries — the  pulse 
— influence  of  disease  on  the  pulse — the  lesser  or  pulmonic — 
the  greater  or  systemic,  circulation— the  capillary  system— in- 
flama  tion— adhesion.  .  .  t 72 


X  CONTENTS. 

CONVERSATION  V. 

Respiration— the  lungs— the  thorax— mechanism  ot  inspira- 
tion—changes wrought  upon  the  air,  by  respiration— relation 
of  these  changes,  to  changes  wrought  upon  the  blood— animal 
heat — respiration  of  Fishes— of  Birds— of  Reptiles— of  Mollusca 
and  Insects— of  Spiders.— Secretion — various  kinds  of  secre- 
tions—secretion  of  the  inferior  animals. — Absorption — perfor- 
med chiefly  by  the  veins— the  lymphatics— the  lymph — nu- 
trition  99 

CONVERSATION  VI. 

Nervous  system.— Its  progressive  developement,  in  the  inferior 
animals— the  spinal  marrow— nerves— brain— functions  of  the 
nervous  system  -  sensation— volition — Mr.  Bell's  discovery- 
theories  of  the  nervous  power— Dr.  Wilson  Philips'  experi- 
ments—phrenology— comparison  between  the  brain  of  man 
and  that  of  inferior  animals— facial  angle— instinct — reason.  .  .  128 

CONVERSATION  VII. 

The  senses-— the  eye— eyebrows— eyelids—eye-lashes— tears — 
sclerotic  coat— choroid— cornea — iris — aqueous  humor — crys- 
talline lens — retina — modification  of  the  rays,  by  the  coats  and 
humors — short-sightedness — motions  of  the  eyes — squinting 
— vision,  assisted  by  the  other  senses — vision  of  Birds — of  Fish- 
es—of  Insects. — Hearing — sound — anatomy  of  the  ear — hearing 
assisted  by  the  other  senses— hearing  of  the  inferior  animals. — 
Smelling — use  of  the  sense  of  smell — smelling;  of  the  inferior 
animals. — Taste — influence  of  civilization  upon  taste — taste  of 
the  inferior  animals. — The  touch — integuments — human  com- 
plexion— albinos. — The  voice — larynx — larynx  of  the  inferior 
animals — cries — language — singing — ventriloquism — voice  of 
Birds 153 

CONVERSATION  VIII. 

Locomotive  organs — bones — composition  of  bone — ossification 
— nutrition  and  reparation  of  bone — joints — skeleton — skele- 
ton of  the  lower  animals — adaptation  of  the  human  skeleton  to 
the  erect  position — human  foot  and  hand — the  muscles— at- 
tachment of  the  muscles  to  the  bones — action  of  the  muscles 


CONTENTS.  XI 

ou  the  principle  of  the  lever — standing — mechanical  contriv- 
ances in  the  leg  of  Birds— walking— leaping — running. -influ- 
ence of  education  on  the  muscles — gymnastic  exe.cises.  .  .  .  197 

CONVERSATION  IX. 

Sleep — necessary  quantity  varied  by  habit,  age,  and  temperament 
— state  of  the  brain  during  sleep— dreaming — somnambulism — 
influence  of  sleep  on  the  other  functions— influence  of  bsbit  on 
the  animal  and  organic  functions  —difference  of  origin— relations 
and  mutual  influence  of  the  functions— laws  of  coexistence 
—death.  .  .  227 


CONVERSATION  I. 


Anatomy— Physiology —  Comparative  Anatomy — Life*— 
Distinctions  between  organic  and  inorganic  bodies — 
between  animal  and  vegetable  beings. —  The  primitive 
tissues — cellular,  muscular  and  nervous  properties  of 
the  tissues — their  elementary  composition. 

Dr.  B. — I  hope,  Emily,  you  have  not  forgotten  the 
arrangements  that  we  made  for  devoting  some  attention 
this  season  to  the  study  of  the  animal  economy. 

Emily. — I  recollect  your  kind  promise,  Dr.  B.,  but 
I  confess  I  do  not  anticipate  that  pleasure  from  the  study 
of  this  subject  which  we  derived  from  that  of  Chemistry 
and  Natural  Philosophy.  My  notions  respecting  it  are, 
perhaps,  vague  and  limited,  but  they  are  of  such  a  dis- 
agreeable and  repulsive  nature,  that  it  really  appears  as 
if  1  could  never  become  interested  in  the  study. 

Dr.  B. — You  have  identified  the  study  of  the  animal 
economy  with  that  of  anatomy,  and  associated  with  it, 
no  doubt,  horrid  ideas  of  dead  bodies  and  mangled  limbs, 
and  all  your  early  impressions  of  "  raw  head  and  bloody 
bones."  You  are  old  enough  now  to  dismiss  such  nar- 
row and  childish  notions,  and  regard  anatomy  as  it  really 
is — the  science  that  unfolds  to  us  a  knowledge  of  the 
noblest  and  most  interesting  works  of  the  Creator.  To 
obtain  a  certain  measure  of  this  knowledge,  it  is  not  ne- 
cessary for  us  to  encounter  the  repulsive  scenes  of  the 
dissecting-room,  or  to  notice  those  numberless  disagree- 
able details  which  are  attended  to  by  professional  men. 
Tl  will  be  sufficient  for  our  purpose,  merely  to  examine 


14  ANATOMY. 

the  most  interesting  results  of  their  researches,  without 
troubling  ourselves  particularly,  with  the  means  and  in- 
struments by  which  they  have  been  obtained. 

Emily. — Will  you  have  the  kindness  to  tell  me  what 
the  nature  and  objects  of  anatomy  are,  for  I  believe  that 
my  ideas  of  this  science  are  extremely  imperfect. 

Dr.  B. — Every  object  in  Nature  is  said  to  be  either 
organized  or  unorganized,  and  these  two  classes  of  bo- 
dies are  distinguished  from  each  other  by  peculiar  modes 
of  structure  and  properties.  Every  organized  body  is 
composed  of  various  parts  or  organs  which  are  all  de- 
pendant on  one  another,  and  whose  mutual  action  is 
necessary  to  keep  the  whole  body  in  existence.  It  is 
the  object  of  anatomy  to  unfold  the  intimate  structure  of 
these  organs,  and  to  ascertain  their  form,  situation  and 
connection  with  one  another.  Defined  generally,  there- 
fore, it  is  called  the  science  of  organization. 

Emily. — I  think  I  have  seen  the  expression,  compara- 
tive anatomy — pray  tell  me  why  this  epithet  is  used  ? 

Dr.  B. — Anatomy  may  be  considered  as  of  two  kinds 
— human  and  comparative.  The  first  is  the  anatomy 
oi  man  ;  the  latter,  of  the  inferior  animals.  It  is  called 
comparative  because  its  results  are  constantly  compared 
with  those  of  human  anatomy,  which  is  taken  as  the 
general  standard  of  comparison.  Now,  I  presume,  you 
can  readily  understand  its  utility. 

Emily. — Yes — for  since  anatomy  generally  is  the  sci- 
ence of  organization,  it  must  evidently  be  better  under- 
stood if  we  extend  our  views  through  the  whole  animal 
kingdom,  instead  of  confining  them  to  the  structure  of 
man  alone.  While  defining  terms,  tell  me  what  is 
meant  by  Physiology,  a  term  that  is  frequently  used  in 
connexion  with  anatomy? 

Dr.  B. — Literally,  it  signifies  the  science  of  nature 
in  general ;  but  in  the  restricted  sense  in  which  it  is  now 
received,  it  means  the  knowledge  of  the  functions,  or 
uses  of  the  various  organs  which  compose  an  organized 
body.  A  more  proper  term  has  been  lately  proposed, 


LIFE. 


and  will  probably  be  ere  long  generally  used  —  Biology, 
or  the  science  of  life. 

Emily.  —  I  have  always  thought  that  I  had  a  suffi- 
ciently correct  idea  of  life,  but  after  the  rigid  precision 
with  which  you  have  defined  your  terms,  I  am  afraid 
that  my  notions  will  prove  rather  indefinite.  The  terms. 
vital  principle,  living  principle,  &c.  have  led  me  to  con- 
sider life  as  something  altogether  distinct,  and  superad- 
ded  to  the  body  ;  in  the  same  manner  as  the  mind  is 
considered  to  be  a  principle  distinct  from,  and  independ- 
ent in  its  existence  of  the  brain. 

Dr.  B.  —  Your  notions  are  erroneous,  but  it  is  not  al- 
together your  fault,  since  they  have  prevailed  among 
medical  men  themselves,  who  have  strangely  mistaken 
an  abstract  term,  for  a  self-existent  and  governing  prin- 
ciple This  mistake,  which  arose,  no  doubt,  from  a 
want  of  precision  in  medical  language,  is  for  this  reason 
unpardonable  now.  By  some  of  the  best  physiologists 
of  the  present  day,  the  term  life  is  used  to  express  the 
general  aggregate  or  combination  of  those  properties 
which  are  peculiar  to  living  beings,  and  which  are  also 
called  living,  or  vital  properties.  The  only  correct  defi- 
nition of  life,  therefore,  would  be  the  enumeration  of 
these  properties,  and  we  can  obtain  exact  and  compre- 
hensive notions  of  it,  only  by  considering  what  these 
properties  actually  are. 

Emily.  —  Do,  Dr.  B.,  explain  them,  for  I  am  impa- 
tient to  know  what  these  curious  properties  are,  that  are 
so  different  from  impenetrability,  divisibility,  attraction, 
&c.  which  are  common  to  all  matter. 

Dr.  B.  —  In  the  first  place  then,  every  organized  body 
is  composed  of  both  solids  and  fluids  which  are  continu- 
ally in  motion  —  continually  acting  on  each  other.  This 
is  necessary  to  the  very  conception  of  a  living  being. 

Emily.  —  But  you  forget  that  crystals  contain  a  cer- 
tain portion  of  water,  which  is  essential  to  their  existence 
as  crystals. 

Dr.  B.  —  But  it  is  water  in  a  solid  state  —  there  is  no 


PROPERTIES 


motion  between  it  and  the  other  parts  of  the  crystal.  A 
second  distinction  between  organized  and  unorganized 
bodies  consists  in  this;  that  the  various  parts  which 
m,;ke  up  the  former  are  different  from  one  another, 
"while  those  of  the  latter  are  perfectly  alike.  If  we. 
break  a  granite  rock  in  pieces,  we  shall  have  every 
fragment  however  small  alike,  except  in  form  and  size 
--  in  every  one  we  shall  find  feldspar,  mica  and  quartz. 
But  if  we  break  in  pieces  a  living  body,  we  have  in  one 
portion,  skin  and  muscle  ;  in  an  >ther,  nerves  and  ves- 
sels ;  in  one,  bark  and  wood  ;  in  another,  leaves  and 
fruit.  The  parts  of  an  unorganized  body,  when  separa- 
ted from  one  another,  still  present  the  same  properties 
as  the  whole  mass.  If  it  be  a  magnet,  every  part  will 
attract  the  needle,  though  with  less  force,  just  as  the 
magnet  did  before  it  was  broken.  But  the  parts  of  an 
organized  body,  when  separated,  lose  the  properties 
which  they  possess  only  when  combined  and  acting  to- 
gether. If  you  tear  a  piece  of  flesh  from  the  body,  or 
an  eye  from  the  socket,  the  one  will  no  longer  feel,  nor 
the  other  see. 

Emily.  —  And  yet  I  have  heard  that  there  is  an  ani- 
mal called  the  Polypus  which  may  be  divided  into  a 
number  of  parts,  and  every  part  will  immediately  be- 
come a  perfect  polypus,  resembling  the  original  in  all 
respects  except  in  size.  This  must  certainly  be  an  ex- 
ception to  your  principle. 

Dr.  B.  —  Before  you  form  your  conclusions  so  hasti- 
ly, you  should  assure  yourself  that  the  facts  are  strictly 
true.  If  you  had  taken  pains  to  obtain  the  true  history 
of  these  creatures  from  scientific  books,  instead  of  adopt- 
ing the  popular  notions,  you  would  have  found  that  they 
were  far  from  being  exceptions  to  our  principle.  The 
plain  truth  is,  that  in  that  class  of  animals  called  Zoo- 
phytes, which  are  the  simplest  of  all  animals  in  construc- 
tion, there  are  many  which  may  be  divided  into  several 
parts,  and  every  part  will  continue  to  live  and  grow,  and 
in  the  course  of  time  will  have  grown  to  the  form,  and 


OF  ORGANIC  BODIES.  I  < 

possess  all  the  properties,  of  the  perfect  animal.  But 
this  requires  time,  and  is  produced  by  a. regular  process 
of  growth  and  developement,  for  immediately  after  this 
division  is  made,  the  parts  are  motionless  and  apparently 
without  life. 

Emily. — Are  not  those  sea-anemones  which  we  ob- 
served yesterday  clinging  to  the  rocks  on  the  beach,  ani- 
mals of  this  kind  ?  I  think  you  said  they  belonged  to 
the  class  of  Zoophytes.  If  they  are,  I  should  like  to  try 
the  experiment  on  those  which  brother  George  brought, 
home.  How  must  they  be  divided  ? 

j}r^  jg. — You  may  divide  them  into  two  portions, 
either  horizontally  or  vertically,  and  after  a  time  you 
will  find  that  both  pieces  have  attained  the  size  and 
form  of  a  perfect  animal.  But  we  must  postpone  these 
experiments  to  a  leisure  hour,  for  recollect  we  are  di- 
gressing from  our  subject. 

Emily. — I  think,  Dr.  B.,  that  I  can  point  out  a  very 
prominent  distinction  between  organized  and  unorgani- 
zed bodies, — the  former  in  the  early  periods  of  their 
life,  are  constantly  growing  in  size,  while  the  latter  do 
not  grow  in  the  least,  but  remain  the  same,  year  after 
year. 

Dr.  B. — True  indeed,  they  do  not  grow  in  the  same 
sense  as  organic  bodies  grow,  but  you  do  not  suppose, 
do  you,  that  minerals  have  never  increased  in  size,  but 
were  created  by  the  great  Architect  just  as  you  see  them. 
Minerals  do  increase  in  size  by  what  is  called  accretion; 
that  is,  by  the  accession  of  new  layers  of  particles  to 
their  surface,  without  any  change  in  their  nature ;  thus 
they  may  be  augmented  to  an  indefinite  extent.  All 
minerals  have  been  formed  in  this  manner,  and  the  pro- 
cess is  continually  going  on,  though  it  may  not  be  appa- 
rent to  us.  Organic  bodies,  on  the  contrary,  grow  by 
assimilation,  as  it  is  termed  ;  they  receive  into  their  in- 
terior various  substances,  all  which,  by  peculiar  powers 
of  their  own,  are  converted  into  one  homogeneous  sub- 
stance, and  carried  to  different  parts  of  the  body.  The 
2* 


IB  PROPERTIES 

active  roots  of  the  plant  absorb  the  nutritious  particles 
from  the  soil,  which  are  transmitted  to  the  leaves,  and 
there  converted  into  a  peculiar  substance  which  furnish- 
es the  secretions  and  nourishing  sap.  The  animal  seizes 
the  heterogeneous  materials  of  nourishment  which  come 
within  its  reach,  dissolves  and  decomposes  them — en- 
dows them  with  new  properties,  and  at  last  renders  them 
fit  to  become  parts  of  the  various  organs  of  which  it  is 
itself  composed.  The  particles  of  which  an  unorgani- 
zed body  is  formed,  are  never  changed  to  give  place  to 
others,  but  continue  with  the  body  as  long  as  it  exsits. 
But  in  organic  bodies,  the  particles  after  a  time  lose 
those  peculiar  properties  with  which  they  were  endowed, 
and  then — being  no  longer  fitted  to  remain  as  parts  of  a 
living  being — they  are  taken  away  and  new  ones  supply 
their  places. 

Emily. — I  will  venture  to  suggest  another  distinction, 
which  I  hope  may  prove  more  fortunate  than  any  other, 
— the  surfaces  of  minerals  are  extremely  rough  and  ir- 
regular,— or  if  regular,  as  they  are  in  crystals,  just  as 
remarkably  smooth  and  even.  Now,  the  surfaces  of  or- 
ganic bodies  are  neither  rough  nor  even,  but  are  more 
or  less  rounded  throughout — the  outline  continually  wav- 
ing. Is  not  this  a  proper  distinction  ? 

Dr.  13. — Yes ;  you  are  perfectly  correct,  and  it  is  on 
this  remarkable  difference  of  the  outline  in  these  two 
classes  of  bodies  that  the  beauty  of  each  depends.  That 
gently  rounded  and  undulating  form  so  beautiful  in  ani- 
mals and  plants,  would  be  a  defect  in  a  crystal — for  this 
pleases  us  solely  by  the  regularity  of  its  angles  and  the 
smoothness  of  its  surfaces. — These  two  classes  of  beings 
are  essentially  different  in  the  manner  of  their  origin.  It 
is  a  universal  law  of  nature,  that  living  beings  derive  their 
origin  from  preexisting  living  beings.  Every  plant  and 
every  animal  supposes  the  existence  of  other  plants  and 
animals,  more  nearly  resembling  them  than  any  other 
objects  in  nature.  All  living  bodies  have  begun  their  ex- 
istence within  other  living  beings,  in  a  rudimentary  state 


OF  ORGANIC  BODIES.  19 

from  which  they  have  gradually  advanced,  and  by  pow- 
ers peculiarly  their  own,  have  been  wrought  into  forms 
of  symmetry  and  beauty.  Life  comet  h  only  from  life. 
Minerals  are  not  produced  in  this  way — they  originate 
merely  from  the  aggregation  or  corning  together  of  parts, 
every  one  of  which  is  as  perfectly  formed,  and  enjoys 
the  same  properties  as  the  combined  mass. 

Emily. — Do  you  really  mean,  that  those  minute  beings 
found  in  vegetable  infusions  and  stagnant  waters  which 
can  hardly  be  perceived  without  the  aid  of  a  glass,  all 
came  from  eggs  that  have  been  layed  and  hatched  by 
parents  resembling  themselves  ?  1  had  always  thought 
they  were  produced  by  the  process  of  decomposition. 

Dr.  B. — Then  I  believe  you  have  always  thought 
wrong.  Recollect,  these  beings  are  minute  only  to  our 
imperfect  eyes.  You  observed  those  on  the  dust  of  the 
fig  by  the  Solar  iYlicroscope,  and  is  it  reasonable  to  sup- 
pose that  such  beings — as  nicely  and  wonderfully  con- 
structed, so  far  as  we  can  see,  as  insects  of  much  larger 
size,  and  as  uniformly  resembling  one  another  in  appear- 
ance— have  been  produced,  not  by  parents  like  them- 
selves, but  at  hap-hazard  iroin  the  diversified  substances 
that  compose  the  dust  of  the  fig  ?  On  the  contrary,  it 
seems  much  more  philosophical  to  believe  that  these 
creatures,  as  well  as  a  vast  many  others  which  were  once 
thought  by  some  to  be  spontaneously  created,  originate 
like  all  other  animals.  Lately,  however,  the  microscope 
has  brought  to  light  some  facts,  which,  if  well  established, 
will  show  that  the  creative  energy  does  not  act  univer- 
sally in  this  way.  But  we  had  better  reserve  our  re- 
marks on  these  discoverie-  for  some  other  occasion. 

Emily. — And  the  termination  of  organic  beings  is  as 
distinctive,  I  suppose,  as  their  origin.  Nothing  like 
death,  I  believe,  happens  to  minerals. 

Dr.  B. — Yes;  death  sooner  or  later  happeneth  to 
every  living  thing — and  this  constitutes  one  of  the  great 
laws  of  organization.  Do  you  not  see  how  death  is  a 
necessary  consequence  of  life  ? 


20  DISTINCTIONS  BETWEEN 

Emily. — Why  really,  I  see  no  absolute  necessity 
which  should  prevent  a  living  being  from  always  pre- 
serving its  freshness  and  vigor,  and  living  on  to  an  indefi- 
nite duration. 

Dr.  B. — True  indeed,  if  you  confine  your  views  to  a 
single  being  isolated  from  all  the  rest  of  creation,  but  not 
when  you  look  at  the  general  economy  of  nature.  The 
materials  suitable  for  the  nourishment  of  living  beings, 
must  at  some  previous  time  have  formed  parts  of  other 
living  beings,  so  that  the  nourishment  of  one  is  obtained 
at  the  expense  of  some  other,  and  thus  necessarily  re- 
quires its  destruction.  Contemplate  at  a  general  view, 
the  countless  forms  of  being  which  crowd  the  vast  do- 
main of  Nature.  Do  you  not  see  the  strong  continually 
preying  upon  the  weak,  and  these  in  their  turn  yielding 
to  others  still  higher  in  the  scale,  and  so  on  through  the 
whole  series — even  from  the  spider  that  entangles  its 
victim  in  its  treacherous  web,  up  to  man  himself,  the 
greatest  destroyer  of  all.  Thus  it  is  in  Nature,  that 
renovation  and  decay — destruction  and  creation — death 
and  life,  follow  each  other  in  constant  and  rapid  succes- 
sion, as  necessary  parts  of  the  great  system  of  the 
universe. 

Emily. — The  characters  you  have  mentioned  are 
common  to  both  animals  and  plants, — are  there  none 
which  distinguish  these  two  classes  of  beings  from  one 
another  ?  • 

Dr.  13. — There  are  several  which  serve  as  general 
characteristics,  but  naturalists  have  hitherto  found  it  very 
difficult  to  find  any  character  which  should  clearly  dis- 
tinguish them  without  any  exception. 

.  Emily. — It  appears  as  if  I  could  very  easily  point  out 
a  distinction ;  for  surely  animals  are  endowed  with  the 
power  of  voluntary  motion,  roaming  about  according  as 
their  wants  or  pleasures  prompt  them  ;  while  plants  are 
immutably  fixed  to  one  and  the  same  spot,  through  their 
whole  period  of  origin,  developement,  and  death — or  if, 
as  is  the  case  in  some  instances,  they  float  about  unat- 


ANIMALS  AND  VEGETABLES. 

taehed  to  any  particular  spot,  it  is  at  the  will  of  the  waves^ 
.not  their  own. 

Dr.  B. — In  a  majority  of  cases,  no  doubt  your  dis- 
tinction will  hold  good,  but  a  little  better  acquaintance 
with  Natural  History  would  iurnish  you  with  abundant 
exceptions  to  it,  as  a  general  rule.  Do  you  not  recol- 
lect those  vast  beds  of  muscles  which  we  observed  the 
other  day  from  the  beach — and  those  little  shell-fish, 
called  Barnacles,  adhering  to  the  piers  of  the  wharfs, 
and  the  bottoms  of  vessels  ?  Not  one  of  these  creatures,, 
as  well  as  a  multitude  of  others  which  might  be  men- 
tioned, ever  move  from  the  spot  where  they  originate. 

Emily. — Well,  Dr.  B.,  no  plant  possesses  feeling, 
whereas  it  is  enjoyed  by  all  animal  beings. 

Dr.  B. — You  are  very  unfortunate  in  the  choice  of 
your  terms,  for  you  could  have  scarcely  found  one  that 
has  been  used  more  indefinitely  than  feeling.  If  you 
mean  by  it  a  consciousness  of  receiving  impressions  from 
without,  it  is  not  peculiar  to  animals, — for  the  motions 
of  many  plants  are  determined  by  the  impressions  of 
surrounding  objects,  in  the  same  manner  as  those  of  a 
multitude  of  Zoophytes.  The  Seaanernone  when  dis- 
turbed, draws  in  its  delicate  feelers  and  retires  as  much 
as  possible  within  itself,  with  no  more  consciousness  of 
impending  danger,  than  the  sensitive  plant,  which,  when 
rudely  touched,  instantly  closes  its  leaves.  If  you  place 
one  of  those  soft,  jelly-like  beings,  called  by  Naturalists, 
Medusae,  and  by  the  sailors  sea-nettles,  sun-fish,  &C.T— 
very  abundant  in  our  waters  in  the  summer  months, — into 
a  vessel  of  water,  and  the  light  be  permitted  to  fall  only 
on  one  side  of  the  vessel,  it  will  constantly  turn  in  that 
direction.  So  too  if  a  plant  be  placed  in  a  darkened 
room  in  which  a  few  rays  are  admitted  by  a  single  aper- 
ture, its  branches  will  imperceptibly  move  towards  it. 
Some  plants  close  their  flowers  at  the  approach  of  rain  ; 
these  medusae  close  themselves  up  from  the  same  cause. 
Thus  you  see  that  in  this  sense,  feeling  is  no  more  an 
universal  characteristic  of  animals  than  voluntary  motion. 


'22  DISTINCTIONS  BETWEEN 

Emily. — Then  of  course  you  will  riot  admit  that  veg- 
etables have  a  consciousness  of  their  existence, — and  yet 
how  can  we  reconcile  it  with  the  goodness  of  the  Crea- 
tor, to  'suppose  that  he  has  cieated  such  a  profusion  of 
life  as  the  vegetable  world  possesses,  without  bestowing 
upon  it  capacities  for  a  greater  or  less  degree  of  happi- 
ness. At  any  rate,  it  is  a  beautiful  theory,  this — that 
the  woods  and  the  fields  are  filled  with  sentient  beings 
that  are  animated,  not  merely  by  the  life  that  supports 
their  existence,  but  by  a  nobler  spirit,  capable  of  con- 
sciousness and  delight. 

Dr.  B. — So  long  as  you  admire  the  picture  for  its 
poetry,  not  for  its  truth,  your  admiration  is  not  mispla- 
ced. The  presumption  of  an  acquaintance  with  the 
designs  of  the  Deity,  which  this  theory  assumes,  is  a 
sufficient  objection,  if  there  were  no  other  to  its  cor- 
rectness. When  we  take  a  survey  of  the  scale  of  be- 
ing, we  see  the  capacities  of  enjoyment  continually  di- 
minishing, until  they  are  entirely  lost  in  the  mineral 
world.  Now,  it  is  no  more  inconsistent  with  the  good- 
ness of  the  Deity  to  have  denied  capacities  of  happi- 
ness to  vegetables,  than  to  have  varied  them  in  animals, 
and  entirely  annihilated  them  in  the  mineral  kingdom. 
Besides,  the  power  of  perceiving  pleasure  and  pain,  con- 
sequently requires  that  of  voluntary  motion,  in  order  that 
its  possessor  may  obtain  the  one  and  avoid  the  other. 
Since  voluntary  motion  has  been  denied  to  vegetables, 
we  must  believe  that  sensation  has  been  withheld  like- 
wise— unless  we  would  impeach  that  very  benevolence 
which  is  adduced  in  favor  of  the  theory.  The  power 
of  perceiving  the  good  and  the  evil,  with  an  inability  of 
pursuing  the  one  and  avoiding  the  other,  has  been  im- 
parted by  nature  to  none  of  her  objects.  'Fanciful  po- 
ets indeed,  in  order  to  excite  our  sympathy  for  helpless 
suffering,  have  represented  the  trees  of  the  forest  as  an- 
imated by  sentient  beings  whose  tears  issue  through  the 
wounds  they  receive. 

A  distinction  that  has  been  strongly  insisted  on  is — 


ANIMALS  AND  VEGETABLES. 

that  in  animals  the  nutriment,  before  undergoing  any  es- 
sential change  is  first  received  into  a  general  cavity  in 
their  interior,  from  which  it  is  absorbed  and  carried  to 
the  various  parts  of  the  body,  while  in  plants  the  nutri- 
tious particles  are  carried  along  through  a  multitude  of 
minute  vessels  which  never  open  into  a  single  general 
cavity.  Many  of  those  animalculae  which  are  produced 
in  vegetable  infusions  are  thought,  however,  to  imbibe 
their  nourishment  from  every  point  of  their  external 
surface.  If  this  be  the  case,  they  are  of  course  ex- 
ceptions to  the  general  rule.  The  corallines  too,  which 
absorb  their  food  from  the  waters  by  their  numerous 
feelers  acting  like  the  roots  of  plants,  must  in  strictness 
be  considered  as  exceptions.  Perhaps  the  best  distinc- 
tion that  has  yet  been  offered,  is  that  of  Mirbel,  founded 
on  the  kind  of  nourishment  adapted  for  their  support. 
We  know  that  plants  alone  have  the  power  of  obtaining 
nourishment  to  a  considerable  degree  from  inorganic 
matter,  such  as  salts,  earths,  airs, — substances  that  are 
certainly  incapable  of  serving  as  food  for  any  animals, 
since  they  invariably  feed  on  organic  matter  either  of  a 
vegetable  or  animal  nature.  So  that  it  would  seem  to 
be  the  office  of  vegetable  life  alone  to  transform  inor- 
ganic matter  into  organized  living  bodies. 

Emily. — I  think  I  could  furnish  an  objection  to  that 
distinction  without  much  difficulty  :  The  earth-worm  has 
nothing  but  earth  to  eat ;  and  the  leech,  I  have  been 
told,  will  live  many  months  on  nothing  but  water. 

Dr.  j?.- — Most  earths  and  water,  contain  in  a  greater 
or  less  degree  particles  of  organic  matter ;  and  it  is 
these  which  furnish  the  principal  nourishment  of  these 
creatures. 

You  must  now  exercise  all  your  faith  till  I  have  time 
fully  to  explain  the  wonderful  truth  which  I  am  now  go- 
ing to  communicate  to  you — all  the  diversified  organs  of 
the  body,  no  matter  how  different  in  density,  color, 
strength,  or  function,  are  every  one  composed  by  the 
various  combinations  and  modifications  of  a  very  few  sin- 


24  CELLULAR  TEXTURE. 

gle  organic  parts,  called  the  primitive  textures  or  tissues.. 
They  are  commonly  reduced  to  three — the  cellular,  the 
7nuscular,  and  the  nervous. 

Emily. — And  do  you  mean  that  the  skin,  hair,  nails, 
bones,  tendons,  nerves  and  vessels,  are  all  formed  out  of 
these  simple  tissues  alone  ?  It  is  inconceivable  to  me 
how  substances  so  different  can  be  composed  ot  pre- 
cisely the  same  constituent  parts.  However,  1  will  mind 
your  caution  and  wait  with  patience  for  a  solution  of  the 
mystery. 

Dr.  B. — Your  haste  prevented  me  from  adding  that 
the  solid  parts  of  the  body  only  were  composed  by  these 
tissues,  and  that  the  solid  parts  of  the  body  bear  a  pro- 
portion to  the  fluids  no  greater  than  1  to  G — some  say 
1  to  10.  The  solids  also  are  not  always  composed  of 
animal  substances ;  for  in  some  of  them  we  find  a 
portion  of  earthly  matter  which  has  been  deposited  by 
the  fluids. 

The  simplest  in  structure,  the  most  abundant  in  quan- 
tity, and  the  most  extensively  diffused,  is  the  cellular 
tissue.  It  enters  into  the  composition  of  every  organ  in 
the  body.  In  a  very  condensed  state  it  forms  the  main 
bulk  of  the  bones,  tendons,  ligaments,  nails,  hair ;  in  a 
softer  and  loser  state,  we  find  it  in  the  skin  and  the  in- 
ternal organs  ;  in  the  form  of  a  thin  membranous  ex- 
pansion, it  serves  as  coats  for  the  vessels  and  sheaths  for 
the  muscular  fibres.  It  fills  up  the  intesstices  between 
the  muscles  and  other  parts  which  lie  near  together,  and 
gives  to  the  whole  surface  of  the  body  that  beautiful 
rour-ded  outline  which  we  were  so  much  admiring.  If 
every  other  portion  of  the  body  could  be  removed  and 
the  cellular  tissue  left  undisturbed  nearly  the  same  form 
and  size  of  the  body  would  remain.  It  is  therefore 
justly  considered  as  the  basis  or  framework  on  which  all 
other  parts  of  the  body  are  built. 

Emily. — But  why  is  it  called  cellular  texture ;  has 
th's  term  reference  to  its  mode  of  structure,  meaning: 
that  it  appears  in  the  form  of  cells  ? 


CELLULAR  TISSUE.  25 

Dr.  B. — Yes,  for  when  closely  examined  by  a  mi- 
croscope after  the  necessary  preparation,  we  observe 
whitish  threads  or  fibres  of  extreme  delicacy — much 
finer  than  the  finest  cobweb — which,  intersecting  one 
another  in  all  directions,  leave  minute  spaces  which  are 
termed  cells,  and  may  be  very  aptly  compared  to  those 
of  the  honey-comb.  These  cells  all  communicate  with 
one  another,  so  that  from  a  single  spot,  the  whole  body 
may  be  distended  with  air  or  water.  This  is  the  reason 
why  the  hands  and  feet  of  dropsical  people  are  more 
inclined  to  be  distended  with  water  than  other  parts — the 
water  gravitating  to  the  lowest  level  it  can  find.  This 
intimate  communication  is  still  more  remarkable  in  regard 
to  air,  for  sometimes  when  an  accidental  opening  has 
been  made  from  the  air-cells  of  the  lungs  into  the  con- 
tiguous cellular  tissue,  the  air  has  penetrated  into  every 
portion  of  it,  and  the  whole  body  become  puffed  to  such 
a  degree  as  almost  to  occasion  suffocation.  Butchers 
are  said,  to  sometimes  give  their  meat  the  appearance  of 
fullness  and  rotundity,  by  blowing  air  into  the  cellular 
tissue. 

Emily. — What  are  its  properties,  Dr.  B.  ?  I  suppose 
that  entering  so  largely  as  it  does  into  the  composition  of 
the  body,  it  must  be  endowed  with  numerous  and  im- 
portant properties. 

Dr.  B. — So  far  however  is  this  from  being  the  case, 
that  out  of  its  four  properties,  not  one  is  of  a  vital  nature, 
but  are  all  common  to  it  and  inorganic  matter.  They 
are  cohesion,  flexibility,  extensibility  and  elasticity. 
This  last  property  is  peculiar  to  the  cellular  tissue  ; 
and  its  operation  in  some  of  the  most  important  actions 
of  life,  are  such  as  to  elicit  our  admiration  at  the  striking 
contrast  between  the  simplicity  of  the  means  and  the 
beauty  and  magnitude  of  the  result.  In  all  cases  where 
accommodation  to  variations  of  capacity,  pressure,  &c. 
is  necessary,  there  we  find  the  cellular  tissue — beauti- 
fully calculated  under  some  one  of  its  numerous  modifi- 
cations, to  answer  any  of  these  diversified  objects.  After 
3 


20  MUSCULAR     TISSUE. 

this  description,  perhaps  you  may  be  able  to  recognise  it 
in  a  quarter  of  beef  or  a  shoulder  of  mutton. 

Emily. — I  presume  it  is  that  delicate,  white  expanded 
substance  which  we  see  in  various  portions  of  its  surface  ; 
and  when  I  pull  asunder  the  fibres  of  the  red  parts  of 
the  meat,  it  appears  in  the  form  of  very  minute  and 
hardly  perceptible  threads,  passing  between  the  fibres 
and  connecting  them  together. 

Dr.  B. — Yes ;  and  these  red  parts  which  constitute 
the  chief  portion  of  meat,  are  formed  by  the  second,  or 
muscular  tissue.  These  fibres,  if  you  will  take  the 
trouble  to  trace  them  out,  will  be  found  to  be  of  consid- 
erable length,  and  arranged  parallel  to  one  another.  A 
mass  of  these  fibres  completely  enclosed  and  separated 
from  the  rest,  in  a  sheath  of  cellular  tissue,  constitute 
what  is  called  a  muscle. 

Emily. — I  do  not  observe  this  sheath  which  you  speak 
of — it  must  have  been  removed  from  these  muscles. 

Dr.  B. — You  may  not  see  it,  perhaps,  since  it  is  so 
exceedingly  thin  and  closely  applied  ;  but  it  really  is 
present.  If  you  move  your  finger  carefully  over  it,  you 
will  find  it  smooth  and  slippery — very  different  from  the 
sensation  produced  by  the  irregular  surface  of  the  naked 
muscular  fibres.  The  fibres  themselves  are  found  to  be 
composed  of  fibres  still  smaller ;  and  if  our  powers  of 
vision  were  sufficiently  great,  we  might  find  these  to 
be  made  of  others  more  minute,  and  so  on  till  we  come 
to  the  ultimate  fibre — that  which  is  susceptible  of  no 
farther  division. 

Emily. — But  does  the  muscular  tissue  always  exist, 
as  it  does  here,  in  the  form  of  long,  thick  masses? 

Dr.  B. — No ;  these  constitute  but  a  portion  of  all  this 
tissue  which  may  be  found  in  the  body.  It  sometimes 
appears  in  a  membranous  form ;  that  is,  in  thin,  broad 
expansions ; « in  a  tubular  form,  it  serves  for  one  of  the 
coats  of  all  the  blood-vessels,  and  is  found  answering  the 
same  purpose  in  the  gullet,  stomach  and  other  cavities 
that  require  occasional  distension. 


CONTRACTILITY.  27 

Emily. — What  a  bright  and  beautiful  red  these  mus- 
cles present ;  pray  what  is  the  cause  of  this  brilliant  hue  ? 

Dr.  B. — It  is  probably  owing  to  a  portion  of  blood 
still  remaining  in  their  vessels,  or  effused  between  their 
fibres.  Whatever  it  may  be,  it  does  not  seem  essential, 
for  by  maceration  in  hot  water  or  alcohol,  they  may  be 
deprived  of  it  without  altering  their  texture  in  the  least. 
The  muscles  of  fishes  are  perfectly  white,  and  so  are 
some  of  those  in  man  which  are  not  in  the  form  of  large, 
fleshy  masses. 

Emily. — Are  the  properties  of  the  muscular  tissue  as 
simple  and  common  as  those  of  the  cellular  ?  It  is  so 
different  in  appearance,  that  I  am  expecting  to  find  that 
its  properties  are  very  different  from,  if  not  more  com- 
plex, than  those  of  the  latter. 

Dr.  B. — Your  conclusion  is  correct.  Muscle,  as  it 
exists  in  the  body  in  connexion  with  the  cellular  tissue 
possesses  both  physical  and  vital  properties.  The  first 
of  these  it  owes  to  the  cellular  tissue,  and  of  course  are 
the  same  as  those  we  have  already  described  ;  but  its 
peculiar  and  specific  property,  is  strictly  of  a  vital  na- 
ture. It  is  called  contractility.  By  virtue  of  this  pro- 
perty the  muscular  tissue  possesses  the  power  of  short- 
ening itself  on  tha  application  of  various  kinds  of  stim- 
ulants. Let  a  fibre  be  exposed  and  pricked  with  a 
needle  or  wet  with  a  drop  of  aqua- fords,  and  you  will 
see  its  two  extremities  approaching  each  other  by  re- 
tracting, and  the  middle  becoming  swollen  and  hard. 
This  property  of  contractility  is  the  source  of  immense 
power 5  it  is  by  muscular  contraction  that  the  various 
movements  of  the  body  are  effected,  as  well  as  some  of 
the  most  important  actions  of  life. 

Emily. — To  tell  the  truth,  Dr.  B.,  I  do  not  see  very 
clearly  how  it  differs  from  elasticity.  The  fibre  it  ap- 
pears, yields  to  the  force  which  is  applied,  and  returns 
to  its  original  condition  when  that  cause  is  removed. — 
Is  there  any  thing  more  in  this  than  what  we  witness  in 
elasticity  ? 


CONTRACTILITY. 

Dr.  B. — You  must  bear  in  mind  that  in  elasticity 
there  is  never  a  real  generation  of  power — the  effect 
produced  is  never  greater  than  the  cause  which  sets  it 
in  action.  In  the  recoil  of  a  steel  spring  there  might  at 
first  sight,  appear  to  be  an  actual  generation  of  power  ; 
but  it  is  a  well-known  fact  that  the  force  with  which  the 
spring  recoils  is  precisely  equal  to  that  which  is  used  in 
compressing  it.  And  so  in  every  piece  of  machinery, 
the  power  produced  is  never  greater  than  that  which 
has  been  expended.  But  in  muscular  contraction 
there  is  a  real  generation  of  power,  for  the  force  with 
which  a  muscle  contracts,  bears  no  proportion  to  that 
by  which  it  is  excited.  If  you  prick  the  internal  sur- 
face of  the  heart  in  an  animal  recently  killed,  it  will 
contract  with  so  much  force  as  to  almost  bury  up  the 
needle  in  its  substance.  See  too,  what  violent  agitation 
you  may  produce  in  the  muscles  of  a  frog,  simply  by 
irritating  them  with  a  pin.  Are  you  not  convinced  now, 
Emily,  that  contractility  is  altogether  different  from  any 
other  property  of  matter  ? 

Emily. — Partially  perhaps,  but  I  am  still  in  doubt 
how  the  fibre  returns  to  its  original  condition,  unless  it 
is  by  its  elasticity, 

Dr.  B. — This  is  probably  produced  by  elasticity,  but 
this  does  not  take  away  the  necessity  of  some  different 
property  to  explain  its  contraction. 

Emily. — But  simple  contractility  merely  shows  the 
fact  that  the  power  of  shortening  itself  is  inherent  in 
the  muscular  tissue  ;  it  does  not  explain  by  what  means 
this  effect  is  produced. 

Dr.  B. — So  many  theories  have  been  published  with 
this  object  in  view,  and  all  so  feebly  supported  by  facts, 
that  it  would  be  hardly  worth  your  while  to  be  made 
acquainted  with  them.  Those  which  have  any  advocates 
now,  make  contraction  to  depend  on  electricity,  or  gal- 
vanism, or  some  change  in  the  chemical  combinations 
of  the  elements  of  the  muscle.  We  cannot  stop  to  dis- 
cuss these  theories — suffice  it  to  say  that  in  the  hands 


NERVOUS  TISSUE.  29 

of  their  several  advocates  they  are  all  plausibly  support- 
ed. It  is  a  singular  fact  in  reference  to  contractility, 
that  though  it  is  generally  very  strongly  excited  by  the 
electric  fluid  after  death,  yet  it  is  entirely  lost  in  a  body 
that  has  been  killed  by  lightning — in  an  animal  that  has 
been  run  to  death,  or  that  has  died  from  the  operation 
of  poisons.  It  has  also  beea  observed  that  the  rapidity 
with  which  putrefaction  takes  place  after  death  is  inverse- 
ly in  proportion  to  the  powers  of  contraction  which 
remain  in  the  muscles.  But  we  must  now  hasten  to  the 
nervous  tissue. 

Emily. — It  is  this,  I  presume,  which  compqses  the 
nerves,  those  curious  organs  that  are  so  much  concerned 
in  the  operations  of  the  mind.  I  promise  myself  much 
gratification  Irom  your  account  of  this  tissue. 

Dr.  B. — It  not  only  composes  the  nerves,  but  the 
brain,  spinal  marrow  and  other  important  parts.  It  has 
a  soft,  whitish,  and  pulpy  appearance,  but  when  properly 
prepared  it  is  observed  to  possess  a  fibrous  structure — 
its  fibres  being  arranged  parallel  to  one  another,  as  in 
the  muscular  tissue.  To  the  nervous  tissue  belongs  the 
general  properly  of  sensibility,  or  the  power  of  transmit- 
ting impressions  that  are  made  on  it,  from  one  part 
to  another.  This,  however,  is  manifested  in  such  differ- 
ent ways  that  there  appear  to  be  distinct  kinds  of  this 
power.  Thus,  a  wound  in  the  head  may  be  followed  by 
sickness  of  the  stomach  ;  in  which  case,  an  impression 
is  communicated  from  one  of  these  parts  to  the  other 
without  the  knowledge  of  the  mind.  This  kind  of  sen- 
sibility is  the  most  common  and  the  most  essential  to 
life.  By  its  influence,  the  various  parts  and  organs  of 
the  body  are  enabled  to  communicate  together,  and  thus 
a  beautiful  harmony  is  maintained  through  all  their  com- 
plicated actions.  Secondly  ;  an  external  object  touches 
the  body  and  an  impression  is  carried  immediately  to 
the  mind  by /which  it  is  made  acquainted  with  the  fact. 
This  h  an  instance  of  a  second  kind  of  sensibility  and  is 
popularly  termed  sensation,  but  is  more  accurately  distin- 
3* 

I 


O  ELEMENTARY  STRUCTURE 

guished  by  the  term  perceptibility.  Thirdly  ;  the  mind 
conceives  the  wish  of  grasping  that  object,  and  an  im- 
pression is  forthwith  transmitted  to  the  hand  which  moves 
in  obedience  to  this  wish.  This  illustrates  a  third  kind 
of  sensibility,  which  in  common  language  is  termed 
volition. 

Emily. — -I  thought  that  volition  was  strictly  a  property 
of  the  mind — an  intellectual  operation,  whereas,  you 
consider  it  if  I  understand  aright,  a  property  of  the  or- 
ganic tissue. 

Dr.  B. — Volition  no  doubt,  originates  in  the  mind — 
there  is  its  fountain-head,  but  since  we  cannot  conceive 
of  its  taking  place  without  the  action  of  the  nervous  tis- 
sue, it  is  more  convenient  to  regard  the  whole  act  as  de- 
pendent on  that  tissue,  leaving  at  rest  the  primary  cause 
by  which  it  is  produced. 

Before  we  close  this  account  of  the  primitive  tissues, 
we  shall  have  time  just  to  notice  very  briefly  their  ulti- 
mate structure.  The  microscopical  discoveries  that 
have  been  lately  made  in  reference  to  the  primitive 
structure  of  the  simple  tissues  are  highly  interesting,  since 
they  throw7  new  light  on  the  nature  oi  organization  in 
general.  All  the  simple  tissues  when  examined  by  a 
powerful  microscope,  after  being  properly  prepared,  are 
found  to  consist  of  an  aggregate  of  minute  filaments  each 
of  which  is  formed  by  a  regular  series  of  globules. 
These  globules  whether  observed  in  the  cellular,  mus- 
cular or  nervous  tissue,  do  not  sensibly  differ  from  each 
other  in  aspect  or  dimensions.  They  are  alike,  also,  in 
all  species  of  animals,  from  man  even  to  the  Zoophyte. 
The  only  difference  seems  to  be  in  the  direction  of  the 
filaments,  which  in  the  cellular  tissue  intersect  each  other 
in  apparently  a  confused  manner.  In  the  muscular  tissue 
the  filaments  instead  of  being  bent  from  their  line  of 
direction,  and  running  into  each  other  are  arranged  in 
parallel  rows,  separate  and  disti.ict  from  one  another.  In 
the  nervous  tissue  the  globules  form  lines  less  zig-zag  in 
their  direction  than  those  of  the  cellular,  but  deviating 


OF  THE  TISSUES.  1 

from  the  parallelism  of  the  muscular  tissue;  not  so 
straight  as  the  one  nor  so  convoluted  as  the  other.  Ob- 
servers differ  in  respect  to  the  size  of  these  globules  ; 
some  say  they  are  one  four  thousandeth,  others,  one  six 
tbousandeth,  and  others  still,  one  eight  thousandeth  part  of 
an  inch  in  diameter.  But  what  renders  these  observa 
tions  peculiarly  interesting  is  the  discovery — made  par- 
tially, indeed  many  years  ago,  but  recently  confirmed  by 
many  new  and  curious  facts — that  if  vegetable  or  animal 
substances  be  macerated  lor  some  time  in  water  at  a 
moderately  warm  temperature,  the  fluid  will  be  found, 
after  a  certain  time,  swrarming  with  animated  bodies  too 
small  to  be  within  the  reach  of  unassisted  sight.  They 
have  been  styled  Infusoria  because  they  have  been  gen- 
erally observed  in  vegetable  infusions.  The  simplest 
form  of  these  creatures  is  that  of  a  ti  ansparent  globule,  so 
small  that  it  appears  to  be  a  mere  animated  point.  They 
have  the  same  Ibrm  and  magnitude  as  the  elementary 
globules  of  which  the  primitive  tissues  are  composed. 

Emily. — But  how  is  it  known,  Dr.  B.,  that  they  do 
really  possess  life  ? 

Dr.  B. — That  fact  is  inferred  by  their  rapid  and  un- 
eeas:!)g  motions  which  have  every  appearance  ol  being 
sjtonianeous. 

Emily. — And  yet  it  is  so  clear  that  these  motions  may 
not  be  occasioned  by  heat,  electricity,  or  some  other 
physical  cause  ?• 

Dr.  B. — We  cannot  say  but  they  are — yet  so  long  as 
the  agency  of  no  physical  cause  with  which  we  are  ac- 
quainted can  be  demonstrated  to  be  present,  we  have  no 
right  to  affirm  its  existence,  if  the  fact  of  their  vitality  be 
strengthened  by  considerable  evidence.  For  microsco- 
pical observations  have  made  us  acquainted  with  other 
minute  beings  differing  from  these  simple  globules  only 
by  a  slight  addition  to  their  structure.  In  one  kind  this 
difference  consists  in  the  addition  of  an  appendage  in 
the  shape  of  a  tail.  Next  above  these  in  the  scale  of 
complexity,  is  another  kind  which  seem  to  consist  of 


32  CLASSIFICATION 

globules  enveloped  in  a  common  membrane  without  any 
opening.  Then  this  form  varies  by  tapering'  at  one  ex- 
tremity into  a  kind  of  tail  or  neck.  Next  we  see1  them 
endowed  with  external  organs,  consisting  of  hairs  or 
bristles.  Again  instead  of  a  cavity  without  an  opening 
as  is  the  case  in  all  that  we  have  yet  described,  we  find 
at  one  extremity  a  distinct  aperture,  thus  forming  the 
first  rudiment  of  an  alimentary  canal.  Next  we  meet 
with  processes  or  lashes  around  the  opening  for  the  pur- 
pose of  propelling  the  fluid  by  their  motion  into  the  ali- 
mentary cavity.  Thus  we  may  go  on  tracing  these 
minute  forms  of  organisation  through  their  increasing 
complexity  until  at  last  we  come  by  these  small  grada- 
tions, to  beings  endowed  with  a  special  digestive  organ 
and  special  organs  of  motion. 

Emily. — We  are  to  conclude  then,  T  suppose,  that 
the  elementary  globules  which  compose  the  primitive 
tissues  are  living  bodies  capable,  when  separated  from 
each  other  of  spontaneous  motions — and  that  it  is  upon 
this  one  simple  organic  point,  that  every  form  of  organic 
matter  is  built  up  from  the  Infusoria  even  to  man  him- 
self. In  truth,  this  is  a  most  interesting  and  curious 
fact. 

Dr.  B. — Such  a  conclusion  would,  no  doubt  be  just, 
were  the  accuracy  of  these  observations  beyond  a  ques- 
tion. But  since  other  naturalists  have  been  unable  to 
verify  them  and  hence  have  doubted  the  ac'curacy  of  their 
results,  we  are  thereby  not  warranted  in  adopting  this 
general  principle. 

Having  now  described  the  primitive  tissues,  our  next 
step  will  be  to  consider  the  several  organs  which  they 
form,  and  the  functions  which  their  organs  accomplish. 

Emily. — If  they  are  numerous,  I  never  shall  remem- 
ber much  about  them  without  the  aid  of  some  classifica- 
tion. May  we  not  divide  the  body  into  head,  trunk  and 
limbs,  and  these  again  into  smaller  divisions  ;  then  we 
should  greatly  facilitate  the  study  of  them. 

Dr.  B. — The  various  organs  are  already  classed., 


OF  THE   ORGANS.  J3 

though  not  according  to  their  relative  situation,  but  ac- 
cording to  the  functions  which  they  perform.  The  su- 
periority of  this  method  of  arrangement  you  will  distinct- 
ly see,  before  we  have  finished  our  studies.  We  find 
several  organs  associated  together  for  the  purpose  of  ef 
fecting  one  general  result  which  is  termed  their  function, 
and  they  are  designated  by  the  name  given  to  that  func- 
tion. Thus,  those  engaged  in  the  process  of  digestion, 
are  called  the  digestive  organs  j  those  engaged  in  res- 
piration, respiratory  organs,  &c.  Again,  we  see  that  the 
general  tendency  of  all  these  functions  is  two  fold — ihe 
nutrition  and  growth  of  the  body  simply,  and  the  connex- 
ion of  the  being  with  the  world  around  it,  by  which  it 
receives  a  higher  and  nobler  existence.  This  forms  two 
general  divisions  of  the  organs  of  the  body  ;  the  first  be- 
ing called  the  organic  functions,  or  functions  of  organic 
life  ;  the  last  the  animal  functions,  or  functions  of  animal 
life.  In  our  next  conversation  WP,  shall  take  up  the  or- 
ganic functions  commencing  with  that  of  digestion. 


34  DIGESTION. 


CONVERSATION  II. 


Digestion — possessed  by  vegetables  as  well  as  animals — 
alimentary  canal — its  coats — the  teeth — mastication — 
lateral  motion  of  the  jaws — deglutition — descent  of 
the  food  into  the  stomach — abdomen — stomach. 

Dr.  It. — The  function  of  digestion  is  that  by  which 
the  various  articles  of  aliment  are  received  into  the  in- 
terior of  the  animal,  converted  into  one  homogeneous 
mass,  deprived  of  some  qualities  and  endowed  with  new 
ones,  and  finally  fitted  to  be  carried  into  the  system  and 
submitted  to  the  operation  of  other  processes  which  pre- 
pare it  for  its  destined  purposes.  It  is  the  most  essential 
function  in  the  whole  animal  economy,  and  seems  to  be 
the  ground  work  of  all  the  others. 

Emily. — According  to  your  definition  then,  the  func- 
tion of  digestion  is  possessed  by  vegetables.  It  is  a 
whimsical  idea  indeed,  to  conceive  of  digestion  without 
a  stomach  or  a  mouth,  though  to  be  sure,  this  method 
has  one  redeeming  quality, — its  possessor  is  never  in 
fear  of  dyspepsia  or  toothache. 

Dr.  J3. — It  is  immaterial  what  names  we  use,  provi- 
ded we  distinctly  understand  their  meaning,  but  since 
the  process  by  which  the  sap  is  absorbed  in  the  roots, 
and  carried  to  the  leaves  where  it  is  converted  into  a  par- 
ticular juice  of  an  entirely  different  nature,  which  sup- 
plies the  plant  with  the  materials  of  growth  and  secre- 
tion, will  come  under  the  definition  that  we  have  given 
of  digestion,  this  term  is  rightly  applied  to  it.  Beside?, ' 


ALIMENTARY  CANAL.  35 

some  of  the  Infusoria  are  as  destitute  of  stomach  and 
mouth  as  vegetables.  But  before  we  speak  particularly 
of  the  digestive  function,  we  will  take  a  slight  glance  at 
the  various  organs  that  are  engaged  in  performing  it. 

Emily. — Pray,  Dr.  B.,  how  many  organs  do  you 
reckon  ?  I  had  no  idea  of  any  other  than  the  stomach, 
and  I  cannot  conceive  why  this  is  not  sufficient. 

Dr.  J3. — It  is  because  you  take  a  partial  view  of  the 
function.  Though  the  most  important  part  of  it  is  per- 
formed in  the  stomach,  yet  there  are  several  auxiliary 
processes  to  be  accomplished  without  which  our  food 
would  be  but  poorly  digested.  Before  it  is  taker  into 
the  stomach  it  must  be  torn  in  pieces  and  chewed  by  the 
teeth  and  mixed  with  the  fluids  of  the  mouth.  Then  it 
requires  to  be  conveyed  to  the  stomach — which  is  ac- 
complished by  the  act  of  swallowing,  the  result  of  a  del- 
icate contrivance  in  the  mouth.  After  it  has  passed 
through  the  stomach  another  cavity  is  prepared  in  which 
it  is  mixed  with  the  bile  and  other  juices,  and  a  system 
of  vessels  to  take  it  up  and  carry  it  into  the  blood. 

Emily. — I  was  not  aware  till  now  of  its  being  such  a 
complicated  process,  though  1  hope  this  will  not  induce 
you  to  abbreviate  your  account  from  the  fear  of  being 
tedious  ;  I  am  sure  J  never  shall  lose  my  interest  in  your 
instructions. 

Dr.  B. — It  will  not  be  necessary  here,  as  well  as  in 
other  parts  of  the  science  to  be  very  minute,  for  there 
are  many  discussions  and  details  wh'ich  it  would  be  use- 
less for  us  to  meddle  with.  We  therefore,  shall  look 
only  to  the  most  important  and  generally  received  views. 
The  digestive  cavity,  or  alimentary  canal  as  it  is  most 
commonly  called,  is  a  long  tube  with  a  high  degree  of 
vitality,  provided  with  the  necessary  apparatus  for  secre- 
ting the  various  fluids  to  be  used  in  the  digestive  pro- 
cess, varying  in  form,  length  and  calibre  according  to 
the  habits  of  the  species.  This  tube  lies  convoluted 
upon  itself,  and  is  of  very  unequal  capacity  in  its  differ- 
ent parts — being  capacious  in  the  mouth,  contracted  in 
the  gullet,  which  again  expands  into  the  stomach,  and 


36  COATS  OF  THE  ALIMENTARY  CANAL. 

then  suddenly  contracted,  it  continues  onward  with  va- 
rious degrees  of  capacity.  In  man,  its  length  is  five  or 
six  times  that  of  the  whole  body.  In  the  inferior  ani- 
mals, we  find  it  larger,  longer,  and  more  complicated 
in  those  whose  food  is  entirely  of  a  vegetable  nature, 
than  in  those  which  are  supported  by  an  animal  nour- 
ishment exclusively. 

Emily. — fs  not  this  because  food  which  has  just  for- 
med part  of  an  animal  body  requires  less  preparation  to 
fit  it  for  nutrition,  than  that  which  is  of  a  vegetable  na- 
ture ? 

Dr.  B. — Your  explanation  is  probably  correct.  The 
walls  of  the  alimentary  canal,  differ  in  its  different 
parts,  in  appearance  and  capacity,  and  are  found  through- 
out their  whole  extent,  to  be  formed  by  two  membra- 
nous coats,  which  though  they  do  not  together  amount 
jto  the  thickness  of  one  eighth  of  an  inch,  are  exceedingly 
strong,  and  by  their  toughness  and  elasticity  are  capa- 
ble of  resisting  a  great  degree  of  force.  The  inner  of 
these  coats  or  that  with  which  the  food  comes  into  con- 
tact, is  called  the  mucous  coat.  Its  appearance  is  dif- 
ferent in  different  parts  of  the  alimentary  canal,  being 
thin  and  smooth  in  the  mouth  which  it  completely  lines, 
thicker  and  more  loosely  applied  in«  the  stomach,  and 
collected  into  transverse  wrinkles,  or  folds  in  the  intes- 
tines. .  It  is  formed  by  cellular  tissue  and  provided  with 
numerous  minute  glands  from  which  a  fluid  is  poured 
out  to  keep  it  constantly  moist.  The  next  coat  is  cal- 
led the  muscular,  and  is  formed  by  muscular  fibres  run- 
ning in  two  different  directions,  one  layer  being  longitu- 
dinal, the  other,  circular.  The  third  coat  called  the 
serous  or  peritoneal  and  external  to  these  two,  is  found 
only  in  some  portions  of  the  alimentary  canal. 

Emily. — I  am  afraid  I  shall  obtain  but  a  poor  idea  of 
these  parts  that  form  the  alimentary  tube  without  some 
plate  or  model. 

Dr.  B. — And  yet,  I  suspect,  you  have  seen  more 
than  once,  what  is  better  than  either  plates  or  models — 
the  object  itself. 


MOUTH.  '0< 

t. — Why  surely  Dr.  B.,  you  cannot  be  serious ; 
I  never  m  my  life  beheld  a  stomach,  nor  any  part  of  one. 

Dr.  B. — Perhaps  not  a  human  stomach.  But  tripe, 
an  article  of  food,  which  no  doubt  you  have  seen  and 
eaten  in  the  course  of  your  life,  is  the  stomach  of  the 
ox,  which,  in  the  same  way  as  man's,  has  these  three 
coats  which  I  have  described.  After  it  has  been  fried 
you  can  easily  separate  them  and  see  their  relative  con- 
nexions. 

Emily. — I  recollect  now  distinctly  the  soft  and  deli- 
oate  appearance  of  the  mucous  coat  and  directly  under 
it,  the  muscular  coat  with  its  red  and  parallel  fibres  very 
perceptible. 

Dr.  B. — As  different  parts  in  the  process  of  diges- 
tion are  performed  in  different  parts  of  the  digestive 
system  of  organs,  it  will  be  convenient  for  us  to  describe 
them  both  in  connexion,  proceeding  in  the  order  in  which 
they  present  themselves. 

Emily. — And  first  I  suppose,  we  have  the  mouth  with 
its  appendages.  Pray  do  be  particular  in  describing  the 
teeth,  for  you  know,  I  have  particular  cause  to  be  inter- 
ested in  their  organs. 

Dr.  B. — Well  then  let  us  look  at  the  mouth  in  the 
first  place.  In  shape,  it  approaches  the  oval  nearer  than 
any  other  figure.  Above  it  is  bounded  by  an  arch  form- 
ed by  a  bone  called  the  palate  ;  below  by  the  tongue  ; 
behind  chiefly  by  the  veil  of  the  palate  and  \hepharynx  ; 
anteriorly  by  the  lips,  and  laterally  by  the  cheeks.  This 
cavity  may  be  greatly  enlarged,  you  know,  by  separa- 
ting the  jaws,  and  the  cheeks,  and  depressing  the 
tongue.  The  upper  jaw  constitutes  a  portion  of  the 
face  and  therefore  moves  only  with  the  head  ;  the  lower 
jaw  on  the  contrary,  is  fixed  by  joints  to  the  head,  and 
is  capable  of  considerable  extent  of  motion — moving 
freely  upwards  and  downwards,  and  a  little  from  side  to 
side.  To  understand  the  admirable  though  simple  con- 
tftYance  by  which  this  lateral  motion  is  effected,  cast 
4 


38  TflETH. 

your  eyes  on  the  branch  of  the  jaw  which  you  see  in  this 
figure  below,  (seep.  40,)  and  observe  how  it  terminates  in, 
a  convex  knob  of  an  oblong  shape,  called  by  anatom- 
ists the  coronoid  process.  These  processes  are  inserted 
into  corresponding  cavities  in  the  head,  just  under  the 
ears.  The  cavities  being  a  little  longer  than  the  process- 
es, these  latter  move  freely  from  side  to  side.  In  the 
jaw  of  a  cat  however,  we  find  that  the  cavity  is  no  lon- 
ger than  the  process,  and  of  course  all  lateral  motion  is 
prevented. 

Emily. — But  why  is  this  Dr.  B  ?  Some  end,  no  doubt, 
is  answered  by  this  peculiar  conformation  of  the  jaw. 

Dr.  B. — Man  does  not  possess  it  exclusively,  but  has 
it  in  common  with  many  of  the  inferior  animals.  If  you 
will  listen  with  patience  till  you  have  learnt  a  little  more 
of  the  other  parts  of  the  mouth,  I  trust  you  will  be  able 
to  explain  the  cause  of  this  difference  without  my  as- 
sistance. As  for  their  structure  the  teeth  differ  from  all 
other  bones  in  superior  hardness,  and  in  having  the  sur- 
face of  the  upper  portion  protected  by  a  thin  layer  of  a 
substance  the  hardest  of  all  others  in  the  body.  By 
means  of  the  enamel  as  this  is  called,  the  teeth  are  effec- 
tually preserved  from  the  influence  of  the  atmosphere 
and  the  chemical  action  of  the  various  secretions  of  the 
mouth.  When  the  latter  are  heedlessly  suffered  to  ac- 
cumulate on  the  teeth,  the  enamel  is  sooner  or  later  de- 
stroyed (for  the  time  depends  on  the  acrimony  of  the 
secretions  which  vary  according  to  the  state  of  the  con- 
stitution,) and  as  it  is  never  renewed,  the  parts  beneath 
are  invaded  and  the  whole  tooth  begins  to  decay. 

Emily. — A  forcible  hint  lor  us,  certainly,  to  cultivate 
assiduously  the  friendship  of  brushes  and  dentifrices,  if 
we  would  avoid  the  attentions  of  the  dentist. 

Dr.  B. — The  portion  ol  the  tooth  below  the  gums  is 
called  the  roots  or  fangs ;  that  above  being  styled  the 
crown  of  the  tooth.  The  enamel  covers  only  the  crown, 
for  the  roots  are  sufficiently  protected  by  the  surrounding 


TEETtf.  39 

parts  in  which  they  lie  completely  and  firmly  imbedded. 
Within  each  root  there  exists  a  canal  leading 
up  into  the  crown  where  they  all  terminate 
in  a  common  cavity,  as  you  may  see  in  this 
figure,  in  which  they  are  represented  by  the 
black  space.     In  these  canals  are  enclosed 
the  nerves  and  blood  vessels  which  serve 
for  the  nourishment  of  the  tooth. 
Emily. — It  is  when  this  cavity  is  exposed  by  disease, 
I  presume,  that  we  experience  that  distressing  affliction, 
the  tooth  ache,  which  too  often  obliges  us  to  resort  to  the 
soothing  properties  of  cold  iron.     Could  not  the  pain  be 
prevented,   and  the  tooth  preserved  by  destroying  the 
nerve  in  some  way  or  other,  as  I  have  sometimes  heard 
proposed  ? 

J}rt  J5. — And  supposing  you  could  succeed  in  the 
operation  of  destroying  the  nerve,  what  would  it  avail 
you  in  the  end  ?  Do  you  imagine  that  the  nerve  is  placed 
there  for  no  other  purpose  than  to  give  pain,  and  that 
the  tooth  can  do  perfectly  well  without  it  ? 

Emily. — I  see  iny  mistake  now,  but  I  never  before 
saw  the  subject  in  that  light.  The  tooth  then  requires 
its  proper  nerves  as  well  as  other  parts,  without  which  it 
tends  to  decay  and  death. 

Dr.  B. — The  teeth,  you  observe,  differ  considerably 
in  their  form  and  size.  In  the  front  of  the  mouth  you 
see  four  in  each  jaw,  rather  flat  and  terminating  in  a 
sharp  edge.  These  are  called  the  incisors  or  cutting 
teeth,  and  are  the  first  to  make  their  appearance  in  the 
young  child.  Behind  these  in  both  jaws  and  on  each 
side  you  may  observe  one  distinguished  from  the  incis- 
ors by  superior  length  and  by  terminating  in  a  point. 
They  are  called  canine  or  dog  teeth,  irom  the  circum- 
stance of  their  being  very  conspicuous  in  the  dog  when 
he  raises  his  lips  under  the  influence  of  anger.  The 
other  teeth  are  much  larger,  their  faces  are  terminated 
by  a  few  blunt  points,  and  he  roots  are  two  or  three  and 
sometimes  four  iq  number.  They  are  called  molares  or 


40 


MASTIFf  CATlGft . 


grinding  teeth,  and  when  all  are  cut  amount  to  twenty, 
making  the  whole  number  of  the  teeth  thirty  two.  The 
last  tooth  in  each  jaw  is  not  cut  till  about  the  twentieth 
year,  and  is  called  the  wisdom  tooth.  The  teeth  are  now 
firmly  fixed  in  the  jaw  in  cells  or  sockets  formed  by  thin 
plates  of  bone  rising  up  from  the  jaw,  as  you  may  see  in 
the  figure  below.  The  only  use  of  these  sockets  is  t« 


contain  the  teeth,  and  when  they  are  no  longer  wanted  in 
consequence  of  the  loss  of  the  teeth,  they  are  absorbed. 

Emily. — Is  not  this  the  cause  of  that  approximation  of 
the  chin  and  nose  so  striking  in  old  people  who  have 
Jost  their  teeth  ?  It  would  seem  that  the  sockets  of  both 
jaws  being  taken  away  the  distance  between  these  two 
parts  of  the  face  must  be  considerably  diminished. 

Dr.  B. — Yes  ;  your  explanation  is  correct.  We  are 
now  prepared  to  consider  the  action  of  the  mouth  on  the 
food,  or  what  physiologists  call  the  process  of  masti- 
cation. The  food  taken  into  the  mouth  is  in  the  first 
place  conveyed  back  and  forlh  between  the  teeth  by  the 
tongue,  the  incisors  cutting  it  in  pieces,  and  the  molares 
grinding  or  breaking  it  down.  This  action  of  the  rnol- 
ares  is  particularly  necessary  when  the  food  consists  of 
grains  or  hard  fruits,  and  you  see  row  how  much  this 
grinding  process  is  facilitated  by  the  lateral  motion  of  the 
jaws. 

Emily. — And  I  suppose  the  reason  why  the  cat  does 
/not  possess  this  lateral  motion  of  the  jaws,  is  that  its 


TEETH  OF  THE  LOWER  ANIMALS.  41 

food  being  raw  flesh,  in  its  wild  state,  it  rather  required 
to  be  cut  or  torn  in  pieces  than  ground,  and  the  upward 
and  downward  motion  of  the  jaws  is  sufficient  for  this 
purpose. 

Dr.  B. — This  is  the  case,  not  only  with  the  cat,  but 
with  all  carnivorous  or  flesh  eating  animals ;  their  mo- 
lares  also  uniformly  terminate  in  sharp  points,  and  their 
incisors  are  long  and  pointed.  In  herbivorous  or  veg- 
etable eating  animals,  on  the  contrary,  the  molar  teeth 
are  much  larger  and  their  faces  present  a  rough  and  ir- 
regular surface,  the  better  to  fit  them  for  grinding  hard 
grains  and  tough  herbage. 

Emily. — Horses,  oxen  and  some  other  animals  ought 
to  have,  I  should  think,  teeth  with  the  power  and  hard- 
ness of  mill-stones,  to  break  down  such  hard,  tough 
substances  as  corn,  hay  and  many  other  articles  which 
they  feed  upon. 

Dr.  B. — Their  teeth  are  admirably  calculated  for 
this  purpose.  They  are  very  large,  and  are  not  only 
surrounded  by  enamel,  but  vertical  plates  of  this  sub- 
stance are  found  in  the  interior  of  the  tooth,  interposed 
with  its  earthy  parts,  and  rising  to  the  surface  of  the 
tooth.  This  prevents  the  tooth  from  wearing  away  as  it 
inevitably  would,  if  the  enamel  were  not  present. 

Emily. — I  recollect  now  having  observed,  when  I 
have  been  looking  at  the  teeth  of  a  horse  or  ox,  several 
undulating,  zig-zag  lines  on  their  surface.  This  is 
caused  I  suppose,  by  the  earthy  substance  being  worn 
away,  and  leaving  the  harder  plates  of  enamel  projecting 
above  them.  But  is  this  the  manner  in  which  the  teeth 
are  always  prevented  from  wearing  away  when  subject 
to  considerable  use  ? 

Dr.  B. — It  is  in  a  great  many  animals,  but  in  the 
gnawing  animals,  such  as  the  beaver,  rat,  squirrel,  &c. 
there  is  a  very  different  contrivance.  To  be  enabled  to 
cut  through  such  hard  solid  bodies  as  they  do  with  per- 
fect ease,  they  are  furnished  with  two "  strong  incisive 
teeth  in  the  front  of  each  jaw.  The  enamel  is  found 
4* 


42          KIND  0V  FOOD  INDICATED  BY  THE  TEETH. 

only  on  the  anterior  surface  of  the  tooth,  so  that  the  pos- 
terior surface  being  soon  worn  down,  the  tooth  has  a 
bevelle'd  edge.  But  without  some  contrivance  or  other, 
this  thin  edge  though  composed  of  enamel  would  yield, 
and  the  tooth  be  at  last  worn  down  to  the  gums.  To 
obviate  these  inconveniences,  the  teeth  are  furnished 
each  with  a  very  long  root  which  grows  upward  and  sup- 
plies the  waste  of  the  crown.  In  some  of  these  animals 
they  have  a  prodigious  length,  extending  backwards  nearly 
to  the  angle  of  the  jaws. 

Emily. — Those  animals  have  no  canine  teeth,  and 
neither,  if  I  am  r.)t  mistaken,  have  the  horse  and  ox  ; 
at  least  there  is  a  space  in  their  jaws  where  the  canine 
should  be,  and  it  is  here  that  the  bit  is  received  in  the 
former  animal. 

Dr.  B. — You  are  right ;  and  not  only  are  the  canine 
sometimes  wanting,  but  also  the  molares.  In  the  dol- 
phins of  various  kinds,  the  teeth  which  amount  frequently 
to  two  hundred  in  number,  are  all  canine.  In  Fishes 
too,  they  are  all  canine.  You  have  seen  many  times 
these  terrible  instruments  in  the  jaw  bones  of  sharks, 
where  the  points  are  extremely  sharp,  and  the  edges 
serrated.  And  to  render  them  still  more  efficacious, 
they  have  the  power  of  raising  or  depressing  them  at  will. 
You  want  no  one  to  teach  you  that  their  food  must  be 
exclusively  flesh. 

Emily. — So  then  by  a  simple  inspection  of  the  teeth 
you  believe  we  may  ascertain  whether  an  animal  lives- 
on  flesh,  or  a  vegetable  diet. 

Dr.  B. — Yes ;  and  where  it  subsists  on  a  mixed  diet 
we  can  tell  with  some  certainty  the  proportion  of  each. 

Emily. — If  that  be  the  case  then,  why  may  we  not 
Bottle  the  long  agitated  question,  whether  man  was  des- 
tined by  nature  to  live  on  an  exclusively  animal  or  vege- 
table diet,  or  on  a  mixed  diet  of  both. 

Dr.  B. — It  cannot  be  determined  from  the  form  of 
die  teeth  only,  for  the  reason  that  nearly  all  the  food  of 
man  except  ripe  fruits,  undergoes  the  preparation  of 


DEGLUTITION.  43 

cookery,  by  which  it  is  so  softened,  that  very  little  neces- 
sity exists  of  much  grinding  or  cutting  powers  in  the 
teeth.  During  mastication,  fluids  are  constantly  poured 
into  the  mouth  from  various  glands  in  the  cheeks  under 
the  tongue,  and  in  fact  from  every  part  of  the  mucous 
membrane.  By  the  saliva  as  these  fluids  are  called,  the 
food  is  moistened,  and  its  comminution  more  easily 
effected— and  perhaps,  a  little  changed  in  its  chemical 
properties.  Being  now  prepared  for  the  action  of  the 
stomach,  let  us  follow  its  course,  and  examine  the  means 
by  which  it  is  conveyed  to  that  organ.  This  process  is 
called  deglutition  or  swallowing,  and  although  apparently 
a  very  simple  thing,  a  distinguished  physiologist  pro- 
nounces it,  "  by  far  the  most  complicated  of  all  the  mus- 
cular actions  which  assist  in  digestion."  To  understand 
it  fully,  let  us  look  first  at  the  parts  which  are  concerned 
in  producing  it.  Attached  to  the  middle  of  the  poster- 
ion  edge  of  the  palate,  you  may  observe  by  looking  into 
your  own  mouth  by  a  mirror,  a  soft,  loose  body  formed 
by  folds  of  the  mucous  membrane,  called  \heveilofthe 
palate,  which  by  means  of  eight  little  muscles  that  are 
inserted  into  it,  may  be  moved  in  a  great  variety  of  di- 
rections. 

Emily. — I  observe  it  distinctly — but  what  are  those 
bodies,  one  on  each  side  of  it,  resembling  it  in  color  and 
apparently  in  texture  ? 

Dr.  B. — Those  are  the  tonsils,  commonly  called  al- 
monds— a  collection  of  mucous  glands.  Passing  on  be- 
tween these,  we,  arrive  next  at  a  sort  of  vestibule  or  cham- 
ber, called  the  pharynx.  In  this  vestibule  we  find  several 
apertures  leading  in  different  directions,  viz.  two  to  the 
nostrils,  called  the  nasal  fossa  ;  one  on  each  side  to  the 
drum  of  the  ear,  called  Eustachian  tubes  ;  one  to  the 
wind- pipe,  called  the  chink  of  the  glottis,  which  is  fur- 
nished with  a  sort  of  valve,  called  the  epiglottis,  capable 
when  shut  down,  of  completely  closing  the  chink.  Seve- 
ral muscles  are  attached  to  the  pharynx,  which  give  to 
it  a  great  variety  of  motion.  Behind,  and  attached  to 


44 

the  pharynx,  is  the  (Esophagus  or  gullet,  a  cylindrical 
tube  lying  near  the  back-bone  in  the  chest,  and  termi- 
nating in  the  stomach.  Now,  when  a  morsel  of  food  is 
ready  to  be  swallowed,  it  is  placed  on  the  superior  sur- 
face of  the  tongue  which  is  then  closely  applied  to  the 
arch  of  the  palate.  The  muscles  strongly  contracting  on 
the  food,  it  is  necessarily  directed  backward,  this  being 
the  only  direction  in  which  it  can  escape  from  the  sur- 
rounding pressure.  Having  now  reached  the  pharynx, 
contrivances  are  obviously  required  to  prevent  it  from 
falling  into  any  of  those  apertures  which  open  into  that 
cavity,  except  the  right  one.  The  veil  of  the  palate, 
therefore,  being  drawn-  back  by  its  muscles,  is  applied 
like  a  valve  over  the  aperture  leading  to  the  nasal  fossa? 
and  Eustachian  tubes,  and  thus  the  morsel  is  effectually 
prevented  from  passing  into  either  of  them. 

Emily. — It  does  pass  through,  sometimes,  notwith- 
standing all  these  obstacles,  for  it  happened  to  myself 
this  morning  while  eating  my  breakfast,  filling  my  eyes 
with  tears,  though  but  the  instant  before  I  was  heartily 
laughing: 

Dr.  B. — And  for  this  very  reason  was  it,  for  when  we 
are  coughing  or  laughing,  and  swallowing  at  the  same 
lime,  the  air  rushing  up  from  the  lungs  through  the  chink 
of  the  glottis,  pushes  the  food  along  towards  the  nasal 
fossae  with  considerable  force. 

Emily. — It  is  prevented  from  entering  the  wind-pipe, 
I  suppose,  by  the  epiglottis  shutting  down,  and  permit- 
ting the  food  to  pass  safely  over  it,  as  upon  a  bridge. 
How  admirably  this  object  is  effected  by  this  beautiful 
contrivance  ! 

Dr.  B. — Withhold  your  admiration  a  moment,  till 
you  are  certain  that  the  cause  of  it  actually  exists, 
^our  explanation  was  the  one  generally  given,  until  it 
was  proved  a  few  years  ago,  by  Majendie,  the  distin- 
guished French  physiologist,  to  be  inadequate  for  the 
purpose.  That  the  epiglottis  shuts  down  as  you  have 
Imagined,  is  undoubtedly  true;  but  Majendie  cutoff  the 


NECESSITY  OF  EXPERIMENTS*  45 

epiglottis  in  several  dogs,  and  found  that  the  creatures 
swallowed  just  as  well  as  before — showing  that  the  ef- 
fect in  question  is  produced  by  some  other  means.  He 
then  divided  the  nerves  which  supply  the  muscles  of  the 
larynx,  by  which  they  were  completely  paralysed,  and 
found  that  deglutition  became  very  difficult,  the  food  fal- 
ling into  the  glottis  and  choking  the  animal.  Hence  it 
followed,  that  in  the  act. of  swallowing,  the  muscles  of 
the  glottis  were  put  into  action,  thus  closing  the  aperture 
and  preventing  the  food  jrom  passing  into  the  wind-pipe. 

Emily. — A  very  satisfactory  result,  no  doubt — but  was 
it  not  very  barbarous  to  subject  so  many  innocent  crea- 
tures to  such  painful  experiments  ?  I  am  sure,  if  phy- 
siology has  been  always  cultivated  with  such  frightful 
means,  my  pleasure  in  its  study  will  be  greatly  dirnirr^ 
ished. 

Dr.  B. — Recollect  that  we  are  constantly  exercising 
that  power  over  the  brute  creation  which  nature  has  put 
into  our  hands,  and  so  long  as  it  is  done  for  good  pur- 
poses, it  is  undoubtedly  well  and  right.  A  whole  spe- 
cies, in  many  instances,  is  condemned  to  incessant  hard 
labor  on  our  account,  and  others  are  raised  for  no  other 
purpose  than  to  be  killed  at  last  for  our  food.  In  com- 
parison then  with  all  this  amount  of  suffering,  of  which 
nobody  complains,  what  are  a  few  experiments,  painful 
though  they  may  be,  the  object  of  which  is  to  enlarge 
the  boundaries  of  human  knowledge.  It  must  be  the 
very  essence  of  maudlin  sympathy  and  short-sighted 
views,  that  would  stigmatize  such  experiments  as  use- 
less and  disgraceful  to  human  nature. 

Emily.- — -I  confess,  Dr.  B.,  I  never  thought  of  it  in  this 
light.  I  am  convinced  now,  that  these  experiments  are 
amply  justified  by  their  utility  in  advancing  the  interests 
of  scientific  knowledge.  But,  pray  go  on  with  your  ac- 
count of  deglutition — I  believe,  we  left  the  food  in  the 
pharynx,  having  got  safely  clear  of  Scylla  and  Charyb- 
dis,  and  ready  for  its  downward  route  into  the  stomach. 

Tb.  B. — The  pharynx  now  contracts  and  pushes  the 


46 


STOMACH. 


food  into  the  gullet.  The  circular  fibres  of  this  organ,, 
stimulated  by  its  presence,  contract  upon  it  and  thrust 
it  onward.  The  next  set  of  fibres,  then  act  and  propel 
the  food  still  farther,  until  by  means  of  this  successive 
contraction  of  the  circular  fibres,  it  at  last  reaches  the 
stomach.  Deglutition  seems  at  first  thought  to  be  per- 
fectly under  our  control,  yet  nearly  all  its  acts  are  en- 
tirely beyond  it,  and  are  purely  instinctive.  The  food 
must  be  of  just  such  size  and  quality,  and  properly  masti- 
cated, before  it  can  be  swallowed,  endeavor  as  much  as 
you  will  to  get  it  down.  Try  to  swallow  your  saliva  five  or 
six  times  in  quick  succession,  and  you  will  see  how  im- 
possible it  is  to  perform  deglutition  by  the  will,  unassisted 
by  any  instinctive  wants.  You  know  how  difficult  some 
people  find  it  to  swallow  a  pill. 

Emily. — I  believe  I  can  testify  to  the  truth  of  that 
fact  myself,  and,  I  am  confident,  you  would  be  the  last 
person  to  refuse  my  testimony. 

Dr.  B. — The  rest  of  the  digestive  operations  take 
place  in  the  abdomen,  the  largest  cavity  in  the  body,  and 
containing,  besides  the  stomach,  many  other  important 
organs.  This  cavity  is  irregularly  egg-shaped,  and 
bounded  on  the  upper  side  by 
the  diaphram  or  midriff,  a 
thin  membranous  muscle,  dis- 
posed in  the  iorm  of  an  arch 
over  the  top  of  the  cavity,  and 
separating  it  from  the  chest. 
Posteriorly  the  abdomen  is 
bounded  by  .  the  back-bone, 
and  anteriorly  and  laterally  by 
the  abdominal  muscles,  the  ac- 
tion of  which  is  likewise  con- 
siderably connected  with  that 
of  the  organs  within.  In  the 
upper  portion  of  this  cavity,  on 
the  left  side,  is  situated  the 
stomach,  a  figure  of  which  you  may  see  in  this  engrav- 
ing. It  is  likened  by  some  to  a  Scottish  bag-pipe  in 


1.  Cardiac  portion  of  the  stomach. 

2.  Pyloric  portion  of  the  itomaeh. 
3. 

4. 

canal 


STOMACH.  47 

shape,  but  may  be  more  accurately  considered  as  a 
conoid  bent  upon  itself.  Into  its  left  and  largest  portion, 
the  oesophagus  enters,  and  this  is  called  the  cardiac 
orifice.  From  the  extremity  of  the  opposite  portion,  we 
see  the  origin  of  the  intestinal  canal ;  the  opening  by 
which  this  communicates  with  the  stomach,  is  called  the 
pyloric  orifice.  The  relation  of  the  stomach  to  the 
surrounding  parts  varies  according  as  it  is  distended 
with  food,  but  it  is  not  worth  our  while  to  notice 
all  these  changes  of  position.  Its  external  or  peri- 
toneal coat  is  reflected  upon  it  from  the  walls  of  the 
abdomen,  but  its  edges,  instead  of  uniting  together 
where  they  meet  on  the  opposite  side,  are  prolonged 
down  some  distance  before  they  unite,  forming  what  is 
called  the  omentum,  or  caul.  Being  liberally  furnish- 
ed with  fat  and  cellular  tissue,  it  lies  down  over  the 
stomach  like  a  curtain,  and  gives  to  this  organ  addi- 
tional warmth  and  security.  The  stomach  is  abundantly 
supplied  with  nerves  and  blood-vessels,  receiving  four 
great  arteries,  three  of  which  are  exclusively  appropri- 
ated to  itself.  So  important  is  this  organ  to  the  living 
economy,  and  so  extensive  and  numerous  are  its  sym- 
pathies with  all  the  others,  that  disease  or  derangement 
in  almost  any  part  of  the  system,  generally  disturbs 
sooner  or  later — sometimes  immediately — the  natural 
harmony  of  its  functoins.  A  single  blow  directly  over 
the  region  where  it  is  situated,  has  been  known  to  pro- 
duce death  with  the  rapidity  of  lightning. 

Emily. — Now,  I  hope  you  are  ready  to  relate  the 
changes  which  the  food  undergoes  in  this  wonderful  or- 
gan. Pray,  what  prevents  it,  if  the  pyloric  orifice  re- 
mains open,  from  passing  directly  down  into  the  intes- 
tinal canal  ?  A  valve,  or  some  other  contrivance,  1  should 
think  was  necessary,  in  order  to  keep  it  closed  while  the 
food  is  digesting. 

Dr>  B- — Do  not  be  impatient ;  you  shall  understand 
it  all  in  due  season.  But,  for  the  present,  we  must  let 
the  subject  rest  till  our  next  conversation. 


48  CHYMIFYCATION. 


CONVERSATION  III. 


Chymiflcation — the  gastric  juice — artificial  digestion— 
digestion  in  Birds — digestion  of  liquids — influence  of 
digestion  on  the  other  functions — effect  of  exercise  on 
digestion — influence  of  the  mind  on  digestion — drinks 
— natural  diet — chyhflcation — bile — liver — pancreas 
— spleen — lacteals — rumination — digestion  of  Rep- 
tiles and  Fishes,  of  Mollusca  and  Zoophytes. 

Dr.  B. — At  last  the  food  1ms  reached  the  the  stom- 
ach, and  the  second  stage  of  the  digestive  process  begins. 
Stimulated  by  the  presence  of  the  food  the  muscular 
fibres  around  the  two  orifices  contract  and  close  them 
up,  and  fluids  poured  out  in  great  abundance  and  mixed 
with  the  mass  of  food.  In  this  state  it  remains  without 
any  perceptible  alteration,  for  a  space  of  time  which 
varies  exceedingly  under  different  circumstances,  though 
when  the  digestion  is  healthy  and  the  food  simple,  it  may 
be  stated  at  about  an  hour.  After  this  time,  a  change 
commences  in  that  portion  in  the  pyloric  part  of  the 
stomach  lying  in  contact  with  the  mucous  coat  by 
which  it  loses  most  of  its  original  properties,  and  is  con- 
verted into  a  soft  homogeneous  substance  of  a  very  dif- 
ferent nature,  called  chyme.  This  substance  has  a 
greyish  appearance,  is  of  a  pulpy  consistence,  has  a 
sweetish  as  well  as  slightly  sour  taste,  and  changes  vege- 
table infusions  to  a  red.  A  general  description  however, 
can  hardly  be  given,  since  it  varies  in  some  degree  accorr 


i'HEOHIES  OF  DIGESTION.  49 

ding  to  the  nature  of  the  aliments,  for  in  fact  there  seems 
to  be  as  "  many  species  of  chyme  as  there  are  varieties  of 
of  food."  The  chyme  when  formed  is  moved  towards 
the  pyloric  orifice  into  which  it  enters,  and  new  portions 
ar<  •  brought  into  contact  with  the  stomach,  until  the  whole 
has  undergone  this  change. 

Emily.- — But  can't  you  say  a  little  more  definitely, 
how  this  marvellous  phenomenon  has  been  produced. 
I  hope  it  is  not  wholly  involved  in  obsurity — if  the  curi- 
osity of  physiologists  has  been  so  strong  as  mine,  I  am 
sure  they  have  not  left  its  extrication  unattempted. 

Dr.  B. — If  you  could  see  but  a  moiety  of  the  discus- 
sions and  speculations  which  this  subject  has  occasioned, 
you  would  be  convinced  that  for  once  at  least,  men  had 
proved  themselves  in  respect  to  that  praise-worthy  spirit 
of  curiosity,  not  unworthy  of  being  mentioned  in  connex- 
ion with  your  own  sex.  The  older  physiologists  were 
utterly  ignorant  of  the  true  nature  of  chymification,  al- 
though they  made  divers  theories  to  explain  it.  Some 
of  them  imagined  it  to  be  a  sort  of  concoction  or  stewing 
of  the  food,  and  this  continued  to  be  a  very  common 
opinion  till  the  revival  of  learning  in  modern  Europe. 
The  chemical  philosophers  who  had  their  day  in  the 
beginning  of  the  last  century,  banished  this  theory  for- 
ever, and  promulgated  the  more  fashionable  one,  by 
which  this  process  was  considered  to  be  neither  more 
nor  less  than  a  true  fermentation.  In  a  short  time  this 
doctrine  was  eclipsed  by  that  of  the  mechanical  philos- 
ophers, who  regarded  chymification  as  nothing  more 
than  mere  trituration  or  grinding,  the  food  being  ground 
up  by  the  walls  of  the  stomach  which  were  thought  to 
be  endowed  with  immense  power.  One  of  the  suppor- 
ters of  the  trituration  theory  even  calculated  the  force 
with  which  the  coats  of  the  stomach  acted  in  digestion, 
which  he  gravely  estimated  at  12,900  Ibs.  The  cele- 
brated Dr.  Hunter  in  his  laconic  way,  has  humorously 
exposed  the  absurdities  of  these  theories,  while  he  has 
pointed  out  their  common  source  of  error.  "  Gentle- 
5 


50  GASTRIC  JUICE. 

men,"  said  he  to  his  class  one  day,  "  some  phisiologists 
will  have  it,  that  the  stomach  is  a  mill ;  others,  that  it  is 
a  fermenting  vat ;  others  again,  that  it  is  a  stew-pan  : 
but  in  my  view  of  the  matter,  Gentlemen,  it  is  neither 
a  mill,  a  fermenting  vat,  nor  a  stew-pan  ;  but — a  stom- 
ach, Gentlemen,  a  stomach."  While  endeavoring  to 
explain  it  on  chemical  and  mechanical  principles,  they 
seemed  to  have  forgotten  altogether,  that  it  is  eminently 
a  vital  process — produced  by  the  action  of  vital  laws. 
The  first  insight  into  the  true  nature  of  digestion,  was 
obtained  by  the  illustrious  Reaumur.  He  attributed 
it  to  the  agency  of  a  peculiar  fluid  found  in  the  stomach, 
being  a  secretion  from  that  organ,  which  is  styled  the 
gastric  juice,  and  though  he  over  estimated  its  singular 
properties,  yet  his  notions  in  the  main  are  correct  and 
have  been,  confirmed  rather  than  discredited  by  time. 
Some  of  the  experiments  that  have  been  made  to  test 
the  powers  of  the  gastric  juice  are  exceedingly  conclu- 
sive. Thus,  a  man  who  was  in  the  custom  of  swallowing 
divers  heavy  and  indigestible  articles  for  his  own 
amusement,  was  made  to  swallow  at  different  times,  hol- 
low metallic  balls  perforated  with  holes  and  filled  with 
meats  of  various  kinds.  These  balls  being  examined 
after  a  certain  time,  their  contents  were  invariably  found 
reduced  to  perfect  chyme.  If  the  gastric  juice  be  the 
sole  agent  in  digestion,  it  must  be  the  most  powerful 
solvent  in  nature,  not  only  dissolving  the  hardest  sub- 
stances, as  bones  and  various  grains,  but  materially 
changing  their  chemical  properties. 

Emily. — I  am  extremely  curious  to  know  the  chemi- 
cal composition  of  this  juice  ;  if  it  corresponds  to  the  im- 
portance and  singularity  of  its  effects,  we  might  expect 
to  find  in  it  some  new  substance  in  nature. 

Dr.  B. — It  has  been  frequently  analyzed,  but  I  be- 
lieve no  substance  has  been  detected  in  it  not  before 
known.  It  is  not  the  same  in  different  animals,  nor  al- 
ways so  in  the  same  individuals,  but  varies  according  to 
the  species  and  the  nature  of  the  food.  It  is  difficult  too. 


GASTRIC  JUICE. 


51 


to  obtain  it  unmixed  with  the  other  secretions.  These 
are  the  causes  of  the  conflicting  results  which  experi- 
ments made  to  ascertain  the  composition  of  the  gastric 
juice,  have  generally  presented.  Later  experimenters, 
by  whom  these  circumstances  have  been  kept  in  view, 
have  found  it  composed  chiefly  of  water,  mucus,  alka- 
line sulphates  (chiefly  soda,)  hydrochlorates,  phosphates, 
muriate  of  lime,  and  a  few  other  salts  in  minute  propor- 
tions. The  acidity  is  occasioned  by  the  presence  of  hy- 
drocloric  and  acetic  acid. 

The  gastric  juice  is  not  only  a  powerful  solvent,  but 
has  remarkable  coagulating  and  anti-putrescent  powers. 
Dr.  Fordyce  states  that  five  or  six  grains  of  the  mucous 
coat  of  the  stomach — from  which  it  is  no  doubt  secre- 
ted— infused  in  water,  gave  a  liquor  which  coagulated 
more  than  a  hundred  ounces  of  milk.  We  find  that 
milk  when  taken  into  the  stomach  is  invariably  coagula- 
ted before  digestion  can  take  place.  Of  its  antiputres- 
cent  qualities  there  is  abundant  proof.  The  fact  has 
been  frequently  verified  by  experiments,  that  putrid  meat 
by  being  introduced  into  the  stomach  of  animals,  will 
after  a  short  time  become  perfectly  sweet.  It  has  been 
ascertained  that  the  gastric  juice  of  the  dog  and  crow 
will  preserve  veal  and  mutton  thirty  days ;  whereas  the 
same  meat  kept  immersed  in  water  will  give  out  a  foetid 
smell  as  soon  as  the  seventh  day,  and  become  perfectly 
offensive  on  the  thirtieth. 

Emily. — I  should  think  that  the  digestive  powers  of 
the  gastric  juice  might  be  satisfactorily  tested  by  obtain- 
ing it  from  the  stomach  of  some  animal,  and  immersing 
different  articles  of  food  into  it.  I  should  be  delighted 
to  witness  its  effects.  Cannot  we  try  the  experiment  ? 

Dr.  B. — We  may  spare  ourselves  that  trouble,  for 
your  idea  has  been  anticipated  long  ago,  by  many  phys- 
iologists. 

Emily. — And  with  what  success  did  they  meet  ? 

Dr.  B. — It  could  not  be  rationally  expected  that  out 
of  the  body,  beyond  the  influence  of  the  vital  powers. 


52  EXPERIMENTS  ON  DIGESTION. 

the  gastric  juice  should  produce  the  same  effects  as  in 
the  stomach.  The  most  that  could  have  been  expected 
is  only  an  approximation  to  the  process  of  digestion,  and 
so  far  late  experimenters  have  fully  succeeded.  Vari- 
ous kinds  of  meat,  bread,  milk,  &c.  which  have  been 
exposed  to  the  action  of  the  gastric  juice  of  the  dog, 
duck,  and  other  animals,  have  been  uniformly,  observed 
to  be  broken  down,  and  the  outer  portions  at  least  chan- 
ged into  a  pulpy  greyish  substance,  resembling  in  ap- 
pearance true  chyme.  Some  very  interesting  experi- 
ments on  the  digestive  powers  of  the  gastric  juice  in 
man,  were  published  a  short  time  since  in  an  Edinburg 
Medical  Journal,  which  were  performed  by  a  surgeon  in 
the  American  army.  The  subject  of  the  experiments 
was  a  young  Canadian,  who,  in  consequence  of  a  wound 
in  the  stomach  occasioned  by  a  musket  shot,  had  an 
external  communication  with  that  organ,  though  at  this 
time  his  health  was  excellent  and  his  appetite  good.  By 
taking  off  the  pad  which  he  wore  over  the  opening,  he 
could  easily  remove  the  aliment  and  his  medical  atten- 
dant frequently  introduced  into  his  stomach  various  sorts 
of  meat  tied  to  a  string,  for  the  purpose  of  observing  the 
changes  produced  by  digestion.  In  one  of  these  experi- 
ments, an  ounce  of  clear  gastric  juice  was  drawn  off  by 
means  of  a  gum-elastic  syphon  into  a  phial  capable  of 
holding  three  ounces.  This  was  about  1 1  o'clock  A.  M. 
and  the  mercury  in  the  tube  of  a  thermometer  introduc- 
ed into  the  stomach,  stood  at  100°  of  Fah.  A  small 
piece  of  boiled  'beef  was  immediately  immersed  in  the 
fluid.  The  bottle  was  well  corked  and  placed  in  a  tem- 
perature of  100°  .  In  about  40  minutes  the  digestioti 
had  evidently  commenced  on  the  surface  of  the  meat* 
At  50  minutes,  the  fluid  in  the  phial  became  opaque  and 
cloudy.  The  fibres  of  the  meat  began  to  be  disengag- 
ed, and  in  one  hour  chyme  seemed  to  be  forming.  At 
P.  M.  the  muscular  fibres  had  diminished  one  half.  At 
5  o'clock,  very  few  remained — and  at  7,  there  was 
scarcely  any  visible  trace  of  muscle.  At  9,  the  whole 


ARTIFICIAL  DIGESTION.  53 

substance  was  completely  dissolved.  The  solution  had 
now  the  appearance  of  whey,  and  shortly  afterwards  a 
precipitate  resembling  the  meat  in  colour  fell  to  the  bot- 
tom of  the  phial.  It  was  now  well  corked  up  and 
showed  no  appearance  of  change,  till  thirty  one  day? 
afterwards,  when  it  exhaled  a  putrid  odour. 

On  the  same  day,  and  at  the  same  hour  apiece  of  meat 
of  exactly  the  same  size  and  kind  as  that  placed  in  the 
phial,  was  introduced  into  the  stomach,  with  a  thread  at- 
tached to  it.  At  the  end  of  one  hour,  it  presented  nearly 
the  same  appearance  as  the  piece  in  the  bottle.  At  one 
o'clock,  the  thread  came  away,  the  meat  appearing  to  be 
entirely  dissolved.  The  process  in  each  case  was  the 
same  for  the  first  hour  ;  but  afterwards  the  meat  was 
more  quickly  digested  in  the  stomach  than  in  the  .phial. 
In  both  cases,  the  digestion  commenced  at  the  surface 
of  the  meat,  and  seemed  stationary  there  for  a  certain 
time.  In  the  phial,  gentle  agitation  seemed  to  quicken 
the  solution,  by  presenting  new  points  of  contact  for 
the  gastric  juice. 

Emily. — Since  then  the  gastric  juice  will  exhibit  its 
peculiar  powers  in  some  degree,  out  of  the  body,  and 
we  are  acquainted  with  its  chemical  composition,  why 
may  we  not  prepare  an  artificial  gastric  juice  that  would 
produce  similar  effects  ? 

Dr.  B. — It  is  probable  that  this  fluid  possesses  vital 
as  well  as  chemical  properties ;  whereas  one  made  arti- 
ficially by  combining  its  constituent?,  would  be  destitute 
of  these  vital  properties.  We  know  perfectly  well  the 
composition  of  the  blood,  but  all  the  chemists  in  the 
world  could  never  make  true  blood  by  combining  its 
constituent  elements.  However,  experiments  of  this 
kind  have  been  tried,  but  they  are  not  yet  complete. 
The  German  experimenters  have  ascertained  that  dilu- 
ted acetic  acid,  diluted  hydrochloric  acid,  a  weak  solution 
of  acetate  of  ammonia,  and  a  solution  of  hydrochlorate  of 
ammonia,  severally  dissolve  more  or  less  of  animal  sub- 


64  STOMACH  OF  BIRDS. 

stances  that  are  used  as  food  ;  but  they  have  not  yet 
tried  their  effects  in  conjunction. 

Emily. — The  gastric  juice  of  the  ostrich,  I  should 
think,  possess  the  solvent  powers  of  aqua  fortis;  for 
I  recollect  reading  an  account  of  one  which  was  brought 
a  few  years  ago  to  New  York,  which  on  one  occasion, 
swallowed  a  pocket  handkerchief,  and  afterwards  swal- 
lowed daily,  gravel,  bits  of  china  ware,  glass,  nails  and 
other  metallic  substances  which  he  picked  up  in  the  yard 
where  he  was  confined.  Its  health  continued  good  du- 
ring the  first  eight  days  after  swallowing  the  handker- 
chief, but  it  soon  lost  its  appetite  and  died. 

Dr.  B. — In  truth,  these  were  truncheon  feats,  which 
modern  gourmands,  resolute  as  they  are,  might  blush  to 
hear ;  unless  we  except  a  hardy  son  of  Neptune  you 
may  have  heard  ol  five  or  six  years  ago,  who  was  ac- 
customed to  swajlow  jacknives  for  his  shipmates'  amuse- 
ment. 

Emily. — This  account  stated,  that  on  examining  the 
ostrich  alter  death,  its  stomach  was  found  quite  full,  and 
distended  by  a  quantity  of  partly  digested  grass,  mixed 
with  corn  and  potatoes  in  a  like  state,  and  a  great  quan- 
tity of  gravel,  glass,  brass  buttons,  old  nails,  and  a  piece 
of  a  small  key.  All  which  appeared  to  have  undergone 
a  strong  friction,  as  if  they  had  been  rubbed  or  polished 
with  a  file. 

Dr.  B. — This  extraordinary  digestion  is  to  be  attribu- 
ted, not  solely  to  the  gastric  juice,  but  also  to  a  tritura- 
ting power  of  the  coats  of  the  stomach  possessed  by  all 
birds  that  live  on  grains  and  other  hard  fruits.  The 
stomach  is  composed  of  strong  fleshy  masses  of  muscle, 
and  possesses  two  distinct  cavities.  The  first  has  the 
form  of  an  irregular  oval,  with  strong,  hard  muscular 
walls,  which  when  in  action  exert  an  astonishing  degree 
of  power.  The  internal  surface  has  the  hardness  of  horn 
itself.  Physiologists  have  been  fond  of  comparing  this 
organ  to  a  mill,  the  tipper  part  resembling  the  hopper,  or 
receptacle  for  the  grain,  and  the  two  projecting  oval  sur- 


DIGESTION  OP  BIKD9. 


55 


faces,  the  mill-stones, — the  intestine  receiving  the  grain 
in  its  divided  state.  It  is  a  mill  too,  which  acts  with  no 
ordinary  power,  as  you  have  seen  in  the  case  of  the 
ostrich.  Spallanzani,  the  Italian  physiologist,  whose 
bold  and  ingenious  experiments  often  astonish  while 
they  convince  the  reader,  has  published  on  this  subject 
sorhe  very  curious  and  interesting  facts.  He  found  that 
balls  of  glass,  and  other  brittle  substances,  when  swal- 
lowed by  some  of  our  domestic  fowls,  were  speedily  re- 
duced to  powder.  Tubes  of  tin-plate  were  also  found 
to  be  crushed  and  broken  down.  Several  leaden  balls, 
each  furnished  with  twelve  sharp  needles,  the  points  of 
which  projected  one  fourth  of  an  inch  beyond  the  sur- 
face, were  introduced  into  the  stomach  of  a  turkey  and 
common  fowl.  At  the  end  of  a  day  and  a  half,  the  ani- 
mals being  opened,  the  needles  were  observed  to  be 
broken  off  close  to  the  surface  of  the  ball.  In  another 
experiment,  he  forced  down  the  throat  of  a  turkey,  a 
leaden  ball  armed  with  twelve  sharp  lancets.  The  crea- 
ture betrayed  DO  uneasiness,  and  being  opened  eight 
hours  after,  the  lancets  were  gone,  leaving  nothing  but 
the  naked  ball  which  presented  some  marks  of  impres- 
sions. The  coats  of  the  stomach  in  all  these  cases  were 
perfectly  unhurt. 

Emily. — Our  common  fowls  seem  to  manifest  a  strik- 
ing fondness  for  such  indigestible  materials,  for  I  have 
frequently  seen  them  swallow  pebbles,  and  it  is  a  com- 
mon notion  that  they  do  not  thrive  when  prevented  from 
obtain  ing  them. 

Dr.  B. — In  these  animals,  they  are  undoubtedly  es- 
sential to  healthy  digestion.  The  quantity  that  is  some- 
times found  in  them  is  truly  astonishing.  Two  hundred 
have  been  found  in  a  turkey- hen,  and  a  thousand  have 
been  taken  from  the  stomach  of  a  single  goose.  But 
we  must  return  to  the  food  which  we  left  changed  into 
chyme. 

Emily. — You  have  not  yet  told  what  change  liquids 
ondergo  when  introduced  into  the  stomach.  The  gas- 


56  DIGESTION  OP  THE  STOMACH. 

trie  juice,  among  its  wonderful  qualities,  cannot  certainly 
have  the  power  of  converting  pure  water,  which  we 
sometimes  drink  by  tumblers-full,  into  real  chyme.  In 
short,  I  do  not  see  but  that  it  must  pass  through  the 
stomach  entirely  unchanged  by  that  organ. 

Dr.  B. — Such  was  the  common  opinion,  till  lately,  it 
has  been  proved  beyond  all  doubt  that,  generally,  liquids 
find  their  way  into  the  system  by  some  other  route.  A 
ligature  has  been  placed  around  the  part  of  the  stomach 
just  above  the  pyloric  orifice,  and  still  liquids  have  dis- 
appeared as  rapidly  as  ever.  Substances  have  been 
found  in  the  blood,  too  soon  after  being  swallowed,  to 
have  reached  this  fluid  by  the  same  passage  as  that 
taken  by  the  food.  When  fluids,  containing  nutritive 
matter,  are  introduced  into  the  stomach,  they  are  either 
coagulated,  as  in  the  case  of  milk,  or  the  liquid  parts  are 
absorbed,  and  the  solids  converted  into  chyme,  as  in  the 
case  of  broths,  gruel,  &LC. 

Emily. — A  difficulty  has  just  occurred  to  me  in  regard 
to  the  solvent  powers  of  the  gastric  juice,  which  to  me 
seems  wholly  inexplicable.  If  what  you  have  stated  be 
true,  I  cannot  possibly  conceive  how  the  stomach  itself 
should  escape  its  power,  for  its  dissolution  appears  to  be 
inevitable. 

Dr.  B. — Your  objection  is  specious,  and  has  given 
rise  to  considerable  unbelief  in  regard  to  our  theory  of 
digestion.  But  the  physiologists  answer  it  by  saying, 
that  the  stomach  is  beyond  the  influence  of  the  gastric 
juice  in  consequence  of  its  own  vitality — when  this  is  lost 
by  the  death  of  the  individual,  it  is  acted  upon  like  our 
ordinary  aliment.  Several  cases  have  been  observed  of 
persons  who  died  suddenly  while  digestion  was  going  on 
and  the  gastric  juice  of  course  secreted  abundantly, 
where  the  coats  of  the  stomach,  having  thus  lost  their 
vitality,  were  found  dissolved  or  corroded  in  a  number 
of  places.  It  has  also  been  ascertained  by  experiments 
that  when  rabbits  were  killed  soon  after  eating  a  quantity 


EXERCISE  AFTER  MEALS.  57 

©f  food,  the  stomach  was  found  to  be  dissolved  in  a  sim- 
ilar way. 

Emily. — What  effects  has  the  process  of  digestion 
on  the  other  functions  of  the  body  ?  From  considering 
its  importance,  and  the  extensive  relations  of  the  stom- 
ach with  other  organs,  it  might  be  expected,  I  think,  to 
be  felt  in  other  parts  of  the  system.  One  thing  is  cer- 
tainly produced — the  feeling  of  a  gratified  appetite  gives 
to  the  mind  a  delicious  sensation  of  tranquillity  and  self 
satisfaction. 

Dr.  B. — The  vital  powers  during  digestion  are  said 
to  be  concentrated  on  the  stomach,  and  hence  that  sense 
of  lassitude  and  drowsiness  which  a  full  dinner  frequently 
occasions.  A  short  nap  at  such  times,  is  to  many  peo- 
ple peculiarly  refreshing,  and  undoubtedly  facilitates  di- 
gestion. There  is  always  more  or  less  reluctance  to 
commence  active  exertion  immediately  after  a  full  meal. 

Emily. — Yet,  Dr.  B.,  a  little  exercise  after  a  meal  is 
popularly  considered  as  conducive  to  health.  At  least 
that  has  been  my  belief. 

Dr.  B. — Physicians  have  generally  eschewed  all  ex- 
ercise directly  after  eating,  chiefly  on  the  strength  of  an 
experiment  periormed  by  Sir  Busick  Harwood.  Two 
pointers  were  fed  on  an  equal  quantity  of  the  same  food 
— one  was  suffered  to  go  to  his  kennel,  and  lie  down, 
while  the  other  was  taken  out  to  hunt.  At  the  end  of 
two  hours  they  were  both  killed  and  examined  ;  when 
in  the  first  the  food  was  found  very  well  digested,  while 
in  the  other  it  was  scarcely  altered.  This  experiment 
however  proves  merely,  that  violent  not  moderate  exer- 
cise, is  unfavorable  to  healthy  digestion. 

But  the  truth  of  the  matter  is  that  the  effects  of 
exercise  after  digestion,  depend  greatly  on  habit  and  con- 
stitution. To  sedentary  people  and  others  who  have  the 
Command  of  their  time,  exercise  after  dinner  is  exceed- 
ingly disagreeable,  though  after  breakfast  or  supper  they 
can  immediately  go  about  their  business  with  alacrity 


58  INFLUENCE  OF  THE  MIND. 

and  vigour.  The  laboring  man  on  the  contrary,  no  soon- 
er swallows  his  meals,  than  he  resumes  his  routine  of 
toil  without  souring  his  temper  or  deranging  his  diges- 
tion. All  this  difference  is  the  result  of  habit.  In  gen- 
eral therefore,  we  may  conclude  that  a  short  period  of 
rest  immediately  after  eating  is  favorable  to  digestion, 
while  various  degrees  of  exercise  may  be  rendered  com- 
patible with  good  health  by  habit  and  temperance. 

Emily. — If  this  then  be  the  case,  eating  a  substantial 
meal  just  before  going  to  bed  at  night,  cannot  be  a  rep- 
rehensible practice,  as  it  is  commonly  considered  ;  since 
the  conditions  most  favorable  to  good  digestion  are  pre- 
sent. 

Dr.  B. — The  popular  opinion  is,  notwithstanding^ 
generally  correct.  The  habit  of  filling  the  stomach  be- 
fore going  to  rest  is  injurious  because  food  is  not  needed, 
and  the  appetite  which  is  feltis  as  artificial  and  as  morbid, 
as  that  which  craves  tobacco  or  ardent  liquors.  '  Why, 
the  very  idea  that  men  whose  employments  are  of  a 
sedentary  nature — for  such  are  the  ones  with  whom  this 
practice  of  eating  second  suppers  is  most  common — need 
a  substantial  meal  four  or  five  hours  after  eating  their 
supper,  is  truly  ridiculous.  This  appetite,  instead  of 
being  created  by  active  exercise  and  temperate  abstem- 
iousness, is  solely  the  result  of  a  long  continued  habit, 
and  veiy  different  from  that  produced  by  the  ordinary 
demands  of  labour.  But  when  food  is  craved  by  an  ap- 
petite created  by  hard  exercise  and  temperate  abstem- 
iousness, it  will  never,  disturb  the  sleep  nor  derange  the 
functions.  The  industrious  farmer  after  finishing  the 
weary  business  of  the  day,  takes  his  evening  repast  and 
retires  immediately  to  his  rest ; — but  whose  sleep  is 
more  refreshing  ?  whose  filled  with  more  pleasant 
dreams  ? 

Emily. — The  function  of  digestion  is  also  influenced, 
if  I  am  not  deceived,  by  the  state  ot  the  mind.  I  have 
known  persons  who,  when  their  attention  has  been  en- 
tirely engrossed  by  some  other  object,  have  forgotten 


COOKERY.  59 

altogether  their  dinner  hour.  I  know  well  enough  my- 
self, that  a  keen  appetite  may  be  instantly  dissipated  by 
the  receipt  of  unpleasant,  news,  or  any  accident  that  oc- 
casions fear  or  anxiety. 

Dr.  B. — Healthy  digestion  always  requires  a  cheer- 
fulness of  disposition  and  a  serenity  of  the  passions. 
When  anxiety  is  clouding  the  mind,  or  some  secret  pas- 
sion preying  upon  its  happiness,  the  appetite  soon  fails, 
food  becomes  loathsome,  a  morbid  irritability  of  the 
stomach  ensues,  and  the  blanched  cheek  and  wasted 
muscle  proclaim  the  origin  and  effects  of  the  disease. 

Emily. — I  need  scarcely  ask,  I  suppose,  whether  the 
usual  drinks  taken  with  our  food  are  the  best  adapted  to 
promote  the  digestive  process.  As  they  are  all  artificial 
and  more  or  less  stimulating,  you  would  say  they  are 
more  injurious  than  beneficial. 

Dr.  B. — We  can  have  no  very  strong  objections  to 
any  but  those  which  contain  a  portion  of  alcohol.  They 
sharpen  the  appetite  no  doubt,  but  it  is  none  but  a  jaded 
and  artificial  appetite  that  needs  such  stimulus.  Pure 
well-water  in  consequence  of  the  salts  which  it  holds  in 
solution  is  perhaps  better  suited  than  any  other  fluid,  to 
dissolve  the  aliments,  and  afford  a  healthy  stimulus  to  the 
digestive  organs. 

Emily. — The  refinements  of  modern  cookery  then  are 
liable  to  the  same  objections,  for  they  are  in  the  highest 
degree  artificial  and  stimulating. 

Dr.  B. — Some  cookery  is  always  required,  before 
our  food  is  capable  of  being  eaten.  But  beyond  this, 
cookery  is  useful,  only  as  it  renders  palatable  and  agree- 
able what  would  otherwise  be  entirely  rejected,  and  it  is 
therefore  conducive  to  economy.  Perhaps  nearly  as 
much  food  is  absolutely  wasted  every  day  in  some  parts 
of  our  country,  as  is  consumed,  for  want  of  a  proper 
knowledge  of  the  art  of  cookery. 

Emily. — And  yet  notwithstanding  all  this  diversity  of 
food,  is  not  the  nutritious  portion — that  which  is  alone 
suited  to  the  nourishment  of  the  body  very  nearly  the 


60  DIET  AS   CONNECTED  WITH  CHARACTER. 

same  in  all  ?  It  is  an  old  saying  that  "  there  are  many 
kinds  of  aliment,  while  there  is  at  the  same  time  but  one 
aliment." 

Dr.  B. — It  is  not  strictly  true  that  the  nutritious  por- 
tions of  all  our  food  are  precisely  alike,  or  capable  of 
being  reduced  to  one  common  principle,  though  no 
doubt  it  is  true  to  a  certain  extent.  Whether  a  per- 
son lives  exclusively  on  vegetable  or  animal  food,  the 
composition  of  the  body  remains  the  same.  Such  also 
is  the  case  with  other  animals.  The  flesh  of  the.  sheep, 
which  lives  entirely  on  vegetables,  and  that  of  the  lion 
whose  only  food  is  raw  flesh,  will  be  found  on  chemical 
analysis  to  be  composed  of  the  same  materials. 

Emily. — But  the  effects  on  their  moral  and  physical 
dispositions  are  by  no  means  the  same,  for  in  one  it  is 
feebleness  and  timidity  ;  in  the  other,  unrelenting  fe- 
rocity and  powerful  strength. 

Dr.  B. — The  diet  of  an  animal,  and  his  moral  and 
physical  disposition  are  far  from  standing  together  in  the 
relation  of  cause  and  effect.  The  fierceness  and  strength 
of  the  lion,  are  inherent  qualities  of  his  nature — compo- 
nent parts  of  his  constitution.  His  digestive  system  is 
capable  of  acting  only  on  animal  food,  and  therefore 
strength  and  fierceness  were  absolutely  necessary  to  en- 
able him  to  obtain  the  proper  means  of  subsistence. 

Emily. — Still,  is  it  not  the  case  with  man,  that  an 
animal  diet  has  a  tendency  to  make  him  strong,  fierce 
and  courageous,  and  a  vegetable  diet  on  the  other  hand 
to  make  him  weak  and  timid  ? 

Dr.  B. — No  doubt  you  have  learnt  this  notion,  as 
you  have  many  others  equally  correct,  from  sources 
which  you  supposed  were  entitled  to  confidence  ;  but 
facts  are  strangely  against  you.  The  Negroes  in  Africa, 
and  the  South  Sea  islanders  subsist  chiefly  on  a  vegeta- 
ble nourishment,  yet  they  are  remarkable  for  physical 
strength,  and  are  not  deficient  in  courage.  The  Esqui- 
maux and  other  Polar  nations,  eat  hardly  any  thing  but 
the  flesh  of  the  seal  and  walrus,  and  drink  their  blood 


INFLUENCE  «F  CLIMATE  ON  DIET.  iil 

warm  from  its  vessels  ;  but  this  diet,  instead  of  assimi- 
lating their  nature  to  that  of  carnivorous  animals,  pro- 
duces a  degraded  condition  both  of  body  and  rnind.* 

Emily. — Do  you  believe,  then,  that  a  vegetable  diet 
is  most  natural  to  man  ? 

J)rf  B. — No  :  I  mention  these  facts,  merely  to  show 
how  erroneous  was  the  notion  which  you  had  adopted. 
All  circumstances  considered,  a  mixed  diet  is  probably 
that  which  is  capable  of  giving  the  most  perfect  devel- 
opement  to  man's  moral  and  physical  powers.  But 
that  nature  has  prescribed  any  particular  diet  for  the 
human  species  generally,  is  a  doctrine  but  feebly  sup- 
ported by  facts.  Man,  unlike  other  animals,  is  not  con- 
fined to  a  limited  district,  and  obliged  to  subsist  on  what- 
ever he  may  find  within  it,  but  has  extended  his  domin- 
ion to  the  uttermost  parts  of  the  earth.  Nature,  no 
doubt,  meant  that  he  should,  for  she  has  given  him  the 
power  of  accommodating  himself  to  the  circumstances 
around  him — to  the  productions,  as  well  as  the  climate 
of  his  abode.  In  the  polar  regions  an  animal  diet  is  ab- 
solutely necessary,  not  more  from  the  impracticability 
of  obtaining  any  other,  than  the  peculiar  condition  of  the 
system  where  all  the  vital  powers  seem  to  have  centred 
in  the  internal  organs,  and  heat,  strong  food,  and  every 
otfyer  stimulus  are  imperiously  demanded  to  support 
them  against  the  influence  of  external  agents. 

Emtiy. — Nor  does  the  demand  seem  to  be  made  in 
vain  ;  behold  the  following  delicate  bill  of  fare  reported 
in  Capt.  Lion's  amusing  journal,  every  particle  of  which 
was  consumed  by  a  young  Esquimaux.  Solids,  lOlbs. 
4  oz. — Water,  1  gallon,  1  pint. — Soup,  1  1-4  pint, — 
Raw  spirit,  31-2  glasses. — Grog,  strong,  one  tumbler  ! 
This  in  twenty-one  hours,  eight  of  which  were  passed 
in  sleep  ! 

Dr.  B. — In  warm   countries,  where  febrile  excite- 
ment is  the  result  of  any   kind  of  stimulus,  vegetable 
food  is  most  conducive  to  the  health  and  vigour  of  the 
6 


LIVER. 


system,  and  there  it  is  that  the  richest  treasures  of  the 
vegetable  kingdom  are  spread  out  in  the  most  generous 
profusion.  The  slaves  in  our  southern  plantations  whose 
diet  consists  entirely  of  Indian  corn,  continue  in  much 
better  condition  and  are  capable  of  performing  a  greater 
amount  of  labour,  than  those  whose  masters  allow  them 
a  quantity  of  animal  food,  and  who  on  the  contrary  are 
weak,  drooping  and  sickly.  We  will  now  follow  up  the 
changes  which  the  food  undergoes  in  its  passage  into  the 
system. 

Emily. — Having  been  fully  converted  into  chyme, 
I  presume  it  passes  on  into  the  intestinal  canal.  I  can- 
not imagine  what  else  can  happen  to  it  before  it  is  pre- 
pared for  the  purposes  of  nutrition. 

Dr.  B. — Now  commences  the  second  stage  of  diges- 
tion, or  that  of  chylifaation,  which  is  produced  chiefly 
by  means  of  the  various  fluids  that  are  poured  out  and 
mixed  with  the  food.  Our  next  step  then  will  be  to  ex- 
amine the  qualities  of  these  fluids  and  the  organs  by  which 
they  are  secreted.  The  most  important  of  them  is  the 
bile,  a  slightly  viscid,  bitter,  and  yellowish  fluid  of  a  very 
compound  nature,  being  at  once  watery,  albuminous, 
oily,  alkaline  and  saline.  The  liver  by  which  it  is  se- 
creted, is  the  largest  viscus  in  the  whole  body.  It  is 
situated  on  the  right  side  in  the  upper  part  of  the  afydo- 
men,  and  is  fixed  firmly  in  its  place  by  several  strong 
ligaments  which  attach  it  to  the  diaphram.  Its  surface 
is  concave  on  one  side  and  irregularly  convex  on  the 
other,  and  is  divided  into  several  lobes  by  deep  fissures. 
What  renders  the  construction  of  the  liver  peculiarly 
remarkable  is,  that  while  like  other  organs  it  has  its  prop- 
er arteries  and  veins,  it  has  unlike  any  of  them  another 
arid  a  complex  system  of  veins.  It  is  called  the  vena 
portce  ;  the  proper  vessels  of  the  liver  are  called  hepatic 
artery  and  hepatic  veins.  The  vena  portae  is  formed  af- 
ter the  following  manner : — all  the  veins  which  carry 
back  the  blood  from  the  intestinal  canal,  stomach,  spleen 


BILE. 


&c.  at  last  unite  into  one  large  vein  and  ascend  towards 
the  liver.  Having  entered  this  it  divides  into  a  multi- 
tude of  minute  veins  that  are  sent  to  every  part  of  it, 
and  the  extremities  of  which  are  said  to  communicate 
with  the  extremities  of  the  hepatic  artery  and  veins. 
What  the  object  of  this  singular  arrangement  can  be,  is 
not  yet  satisfactorily  determined.  By  some  it  is  thought 
that  the  blood  brought  to  the  liver  by  the  vena  portae  is 
that  from  which  the  bile  is  secreted,  and  that  the  use  of 
the  hepatic  artery  is  only  to  nourish  the  organ.  Others 
believe  that  the  hepatic  artery  furnishes  not  only  the  ma- 
terials of  its  own  nourishment,  but  those  for  the  secretion 
of  bile, — that  the  vena  portae  abounds  with  the  products 
of  digestion  which  have  been  absorbed  from  the  intestinal 
canal,  and  are  subjected  to  the  action  of  theliver  in  order 
that  the  useless  portions  may  be  separated  from  them  and 
the  rest  receive  a  higher  degree  of  animalization.  Neith- 
er of  these  opinions  is  supported  by  direct  proof,  though 
the  latter  is  rendered  quite  plausible  by  numerous  analo- 
gies. 

The  bile,  as  fast  as  it  is  formed,  is  transmitted  drop 
by  drop  by  its  proper  duct  into  the  intestinal  canal.  This 
duct  communicates  with  a  small  membranous  sac,  called 
the  gall-bladder,  which  contains  a  quantity  of  bile  a  lit- 
tle changed  in  its  properties,  being  of  a  greenish  colour, 
less  watery,  and  more  bitter  and  acrimonious.  It  is  gen- 
erally considered  as  a  reservoir  for  the  bile,  when 
digestion  is  not  going  on,  and  its  presence  consequently 
not  wanted.  This  view  of  its  use  however,  is  not  uni- 
versally received,  but  as  the  subject  is  yet  very  obscure, 
it  would  be  time  unprofitably  spent  to  detain  you  with 
any  farther  speculations.  Whatever  may  be  its  use,  we 
may  be  confident  that  it  is  not  essential  to  the  animal 
economy,  for  in  many  quadrupeds,  the  deer  for  instance, 
it  is  found  wanting. 

Emily. — Are  physiologists  any  better  acquainted  with 
the  use  of  the  bile,  than  they  are  with  the  manner  in  which 


V4  PANCREATIC  JUICE, 

it  is  produced  ?  It  certainly  seems  to  be  destined  for 
some  important  purpose,  from  the  complicated  system 
of  means  used  for  its  production,  and  its  being  mixed 
with  the  chyme  immediately  after  it  has  left  the  stom- 
ach. 

Dr.  B. — That  it  is  not  merely  an  exerementitious  or 
refuse  fluid,  but  is  eminently  serviceable  in  digestion  in 
some  way  or  other,  is  now  pretty  generally  admitted. 
But  as  to  the  precise  part  which  it  accomplishes  in  the 
process,  we  are  rather  in  the  dark.  Some  have  thought 
that  it  acts  merely  as  a  healthy  stimulus  to  the  diges- 
tive organs;  others,  that  it  produces  those  chemical 
changes  on  the  chyme  by  which  it  is  converted  into 
chyle.  In  support  of  this  latter  notion  some  experiments 
are  advanced  in  which  the  gall  duct  was  tied,  so  that  the 
bile  was  prevented  from  flowing  into  the  intestinal  canal, 
and  the  effect  upon  digestion  which  was  about  to  com- 
mence, carefully  observed.  In  all  these  cases,  the 
chyme  was  perfectly  well  formed  in  the  stomach,  but  the 
second  stage  of  digestion,  or  the  conversion  of  chyme  in- 
to chyle,  was  instantly  prevented — as  no  chyle  was  found 
in  the  intestinal  canal,  but  a  semi-fluid  substance  very 
nearly  resembling  chyme. 

Emily. — But  is  the  bile  the  only  agent  of  chylifica- 
tion  ?  I  thought  you  mentioned  that  there  were  several 
jfiuids  poured  into  the  intestinal  canal  to  assist  in  perform- 
ing this  process. 

Dr.  B. — There  is  one  other  special  fluid  yet  to  be 
mentioned,  which  is  secreted  by  an  organ  called  the 
pancreas.  It  is  situated  in  the  back  and  upper  part  of 
the  abdomen  behind  the  stomach,  and  resembles  in  struc- 
ture the  salivary  glands  in  the  mouth.  The  fluid  which 
it  secretes,  likewise  resembles  the  saliva  and  is  transmit- 
ted to  the  intestinal  canal  by  its  proper  duct  which  en- 
ters it  with  the  duct  of  the  liver.  What  its  exact  use  is, 
is  not  known ;  though  there  can  be  no  doubt  that  it  is 
highly  necessary  in  the  process  of  chylification,  since 


SPLEEN. 


65 


extreme  emaciation  always  accompanies  a  disease  of  this 
organ. 

The  mucous  membrane  secretes  a  peculiar  fluid 
which  undoubtedly  bears  some  part  in  the  process  ol 
digestion.  Haller  called  it  the  intestinal  juice,  and 
thought  that  eight  pounds  of  it  were  secreted  in  the 
course  of  twenty  four  hours.  It  has  not  been  carefully 
analyzed,  and  we  are  rather  ignorant  of  its  properties. 

It  may  be  well  to  mention  here  the  spleen,  which, 
though  it  is  generally  classed  with  the  digestive  organs, 
has  at  one  time  or  another,  been  imagined  to  have  a  share 
in  almost  every  function  of  the  body.  Some  of  the 
theories  which  have  been  made  to  explain  the  use  of  the 
spleen,  are  truly  rather  calculated  to  excite  a  smile  than 
invite  a  serious  examination.  One  old  physiologist  hav- 
ing observed  it  uncommonly  large  in  persons  addicted  to 
immoderate  laughter,  forthwith  concluded  that  the  spleen 
was  the  seat  of  that  propensity  ;  others  on  the  contrary, 
were  confident  that  it  was  the  seat  of  that  moral  affec- 
tion whose  name  it  bears.  Some  have  supposed  that  it 
acted  as  a  sort  of  wastegate,  to  receive  the  superfluous 
blood  of  the  stomach  when  not  required  by  that  organ  ; 
while  others  have  thought  it  was  the  liver  for  which  it 
served  this  purpose.  One  thought  its  office  was  to  form 
the  red  globules  of  the  blood,  and  another,  as  if  to  give  it 
an  extent  of  influence  proportioned  to  the  trouble  and 
vexation  which  it  had  occasioned  to  inquisitive  physiolo- 
gists, declared  that  its  sole  use  was  to  secrete  the  wax  in 
the  ear.  Another,  after  a  deliberate  examination  of  the 
subject,  came  to  the  sagacious  conclusion,  that  it  had  no 
particular  use  at  all,  but  an  empty  space  being  left  after 
the  formation  of  the  other  organs,  this  was  puf  in  to  keep 
every  tiling  snug  and  tight.  Its  use,  whatever  it  may 
be,  does  not  seem  to  be  essential  to  life.  It  has  beea 
removed  from  dogs,|without  any  particular  inconvenience, 
and  in  one  instance  it  was  taken  from  a  man  in  conse- 
quence of  a  wound,  who  recovered  and  did  very  well. 
6* 


CHYLE. 


Emily.  —  What  are  the  qualities  of  the  fluid  which  it 
secretes  ?  I  should  imagine  that  this  might  give  some  in- 
sight into  its  use. 

Dr.  B.  —  If  the  spleen  does  secrete  any  particular 
fluid,  it  is  not  carried  away  by  any  secretory  duct.  It 
seems  probable,  from  the  latest  experiments,  that  it  is 
connected  with  some  other  function  than  digestion. 

On  being  mixed  with  the  bile  and  pancreatic  juice, 
the  chyme  acquires  a  more  yellowish  colour,  its  taste  is 
more  bitter,  and  its  sharp  odour  is  essentially  diminished. 
Soon  we  find  it  distinguishable  into  two  portions,  one  a 
whitish,  milky  substance  swimming  on  the  surface,  which 
is  called  chyle,  and  the  other,  the  greatest  in  quan- 
tity, a  yellow  pulp.  The  latter  consists  of  those  portions 
of  the  aliment  that  are  incapable  of  assimilation,  and  are 
destined  to  be  removed  from  the  system  ;  the  former 
has  received  a  certain  degree  of  animalization,  and  is 
now  ready  for  the  other  changes  that  are  to  prepare  it 
for  nutrition. 

Emily.  —  Truly,  we  have  a  strange  and  wonderful 
machinery  within  us,  that  can  thus  work  such  a  meta- 
morphosis in  the  meat  and  bread  that  we  eat. 

Dr.  B.  —  And  the  complete  metamorphosis  is  not  yet 
accomplished  ;  many  more  changes  still  are  to  be 
wrought  upon  it,  before  the  materials  of  our  food  are 
properly  fitted  for  becoming  component  parts  of  the  liv- 
ing being. 

Emily.  —  I  had  forgotten  that  the  chyle  was  yet  to  be 
disposed  of;  but  I  cannot  possibly  conceive  what  be- 
comes of  it.  That  it  must  be  carried  out  of  the  intesti- 
nal canal  is  very  obvious,  because,  being  destined  to 
replenish  the  natural  losses  of  the  system,  it  would  be 
useless  for  it  to  remain  there. 

Dr.  B.  —  Certainly  it  would,  and  therefore  we  find 
an  admirable  provision  for  transmitting  the  chyle  as  soon 
as  it  is  formed,  from  the  intestinal  canal  into  the  blood 
vessels.  If  an  animal  be  examined  in  the  course  of  an 


LACTEAL*.  67 

hour  or  two  after  eating,  we  shall  observe  a  great  num- 
ber of  extremely  small  vessels  arising  by  imperceptible 
orifices  from  the  surface  of  the  mucous  membrane,  and, 
from  the  milky  appearance  of  the  fluid  contained  in 
them,  called  lacteals.  As  they  pass  off  from  the  intes- 
tines, they  unite  together  and  form  larger  trunks  ;  these 
proceed  backwards  towards  the  spine,  where  they  meet 
with  a  number  of  irregularly  shaped  bodies,  called  the 
mcsenteric  glands,  in  which  they  are  ramified  to  extreme 
minuteness.  From  these  glands,  come  out  several  ves- 
sels larger  than  the  lacteals,  but  very  similar  to  them  in 
appearance.  These  at  last  join  in  one  common  trunk, 
Galled  the  thoracic  duct.  This  vessel  is  about  the  size 
of  a  goose-quill ;  it  lies  along  the  spine  running  from  the 
abdomen  up  through  the  chest,  till  it  terminates  in  one  of 
the  veins  of  the  left  arm.  To  recapitulate  in  one  sen- 
tence the  course  of  the  chyle  ; — it  is  taken  up  from  the 
small  intestines  by  the  mouths  of  the  lacteals ;  carried  by 
them  to  the  mesenteric  glands,  where  some  change  with 
which  we  are  not  yet  acquainted,  is  wrought  upon  it ; 
thence  into  the  thoracic  duct,  which  at  last  pours  it  into 
the  veins,  where  it  becomes  mingled  with  the  mass  of  the 
blood. 

Emily, — You  speak  of  the  chyle  being  absorbed  by 
the  lacteals,  as  if  they  exercised  a  sort  of  intelligence  in 
the  process.  I  do  not  exactly  comprehend  your  idea. 

Dr.  B. — The  principles  upon  which  the  lacteals  se- 
lect the  chyle  from  the  mass  of  heterogeneous  materials 
with  which  it  is  mixed,  have  been  variously  explained 
by  physiologists.  In  this  respect,  the  lacteals  seems  to 
be  analogous  to  the  fibrils  of  the  roots  in  plants,  which 
absorb  from  the  soil  those  substances  only  which  are 
proper  for  the  nourishment  of  the  plant.  We  witness 
the  fact,  but  in  attempting  to  explain  it,  we  can  go  no 
farther  perhaps,  than  to  attribute  it  to  the  operation  of 
vital,  not  mechanical  principles. — Such  is  a  general 
sketch  of  Digestion  in  man  and  a  few  other  animals  that 


(53  RUMINATION. 

nearly  resemble  him  in  structure.  But  the  truly  philo- 
sophical mind,  whose  object  in  the  study  of  nature  is 
the  attainment  of  general  views,  not  insulated  facts,  will 
not  rest  satisfied  here,  but  will  wish  to  contemplate  this 
wonderful  function  in  the  other  orders  of  being  that  fill  up 
the  great  scale  of  animal  existence.  In  the  study  of  the 
animal  economy,  nothing  can  be  more  interesting  than 
to  trace  the  various  changes  which  the  functions  of  life 
undergo,  as  we  follow  down  the  constantly  varying  forms 
of  organization,  from  the  most  perfect  and  complicated, 
to  the  most  simple  and  rudimentary, — to  see  how  some 
new  modification  is  continually  occurring  to  correspond 
with  other  peculiarities  of  structure,  but  still  answering 
the  same  ultimate  purpose, — to  behold  the  organs  stead- 
ily diminishing  in  complexity,  till  at  last  they  are  one 
alter  another  totally  annihilated. 

Emily. — Such  general  views  of  the  vital  functions 
must  certainly  give  us  a  worthier  idea  of  the  wonder 
and  glory  of  Nature's  works,  than  to  behold  them  in  one 
order  of  beings  alone.  After  considering  them  as  they 
exist  in  the  human  structure,  no  one  can  help  being 
gratified  at  seeing  how  curiously  they  are  varied,  so  as 
to  correspond  with  the  varying  structure  and  circumstan- 
ces of  the  animal. 

Dr.  B. — In  the  quadrupeds,  or  mammiferous  ani- 
mals, as  they  are  called  by  naturalists,  the  organs  of  di- 
gestion very  nearly  resemble  those  of  man.  In  one  order, 
however,  the  cloven-footed  ai?!.nals,  such  as  the  ox, 
deer,  sheep,  &,c.  there  is  a  curious  modification  of  this 
function,  the  design  of  which,  or  its  relatton  to  the  gene- 
ral organization  of  the  animals,  is  not  very  apparent. 
They  possess  four  stomachs,  the  first  three  of  which 
communicate  directly  with  the  oesophagus.  After  the 
food  has  been  partially  chewed  in  the  mouth,  it  is  swal- 
lowed and  received  into  the  first  stomach.  There  it  is 
mixed  with  the  fluids  that  are  poured  out  abundantly 
from  its  internal  surface,  and  by  this  means,  and  proba- 


DIGESTION  OF  INFERIOR  ANIMALS.  69 

bly  by  the  motions  of  the  organ  itself,  it  is  softened,  di- 
vided and  formed  into  little  pellets.*  By  the  contrac- 
tions of  the  stomach,  these  are  made  to  ascend  the  oeso- 
phagus to  the  mouth,  where  they  undergo  a  second  and 
more  thorough  mastication.  Thence  it  is  carried  di- 
rectly to  the  second  stomach,  where  it  experiences  some 
further  changes,  the  nature  of  which  is  not  exactly  known, 
and  then  passes  on  into  the  third  and  fourth  stomach. 

Emily. — I  have  frequently  observed  cows  chewing 
their  cud,  when  they  seemed  to  be  in  quite  a  compla- 
cent, meditative  mood. 

Dr.  B. — It  is  from  this  appearance  of  meditation 
which  they  exhibit  while  chewing  the  cud,  that  they 

have  derived  the  name  of  ruminating  animals. In 

Birds  we  noticed  a  curious  peculiarity  in  the  form  of 
the  stomach,  by  which  it  is  endowed  with  great  strength 
and  powers  of  trituration.  But  this  is  not  the  only  pecu- 
liarity which  they  possess  in  their  digestive  organs.  In 
those  which  live  on  grain  and  other  hard  substances, 
there  is  a  membranous  sac  in  the  neck  communicating 
with  the  oesophagus,  called  the  crop,  or  craw.  Into  this 
receptacle  the  food  is  conveyed,  and  softened  by  the 
fluids  secreted  from  the  glands  with  which  it  is  furnished 
— thence  it  is  carried  to  the  stomach.  In  some  of  the 
carnivorous  birds,  this  sac  seems  to  be  merely  a  dilata- 
tion of  the  oesophagus,  and  serves  as  a  reservoir  in  which 
they  carry  their  food  when  not  immediately  required. 

In  the  Reptiles  and  Fishes,  there  is  nothing  particu- 
larly remarkable  in  the  structure  of  their  digestive  or- 
gans. They  are  fitted,  in  most  of  these  animals,  to  di- 
gest flesh,  and  the  constitutional  sluggishness  of  the  for- 
mer enables  them  to  abstain  from  food  for  a  considera- 
ble time.  Some  of  the  turtles  go  months  and  even 

*  The  author  has  preferred  to  follow  Toggia's  account  of  rumina- 
tion— opposed  as  it  is  to  (hat  of  Blumenbach,  Curvier,  &c.  and  not  yet 
perhaps  generally  adopted — because  it  appears  to  be  the  most  philo- 
sophical explanation  of  this  process,  and  the  best  supported  by  facts, 


TO  DIGESTION   OF   ZOOPHYTES. 

years  without  eating.  Their  voracity  is  sometimes  al- 
most incredible.  The  Boa  constrictor  and  Anaconda 
swallow  animals  nearly  as  large  as  themselves,  and  af- 
terwards retire  to  some  obscure  place,  and  remain  in  a 
state  of  stupid  inaction  while  the  process  of  digestion  is 
going  on. 

In  the  Mollusca,  or  shell-fish,  the  organs  of  digestion 
present  considerable  variety  of  structure.  Some  of  them 
only  have  jaws  for  mastication.  Some  are  provided  with 
a  crop,  and  a  muscular  or  membranous  stomach  as  in 
the  Birds,  and  they  are  probably  used  for  the  same  pur- 
pose. Those  without  a  head,  as  the  clam,  oyster,  &ic. 
feed  only  on  such  nutritious  matters  as  are  brought  to 
them  in  the  water.  The  lobster,  crab,  &e.  are  remark- 
able for  having  their  teeth  placed  in  the  stomach  instead 
of  their  jaws. 

Emily. — -An  arrangement  wThich  has  one  convenience 
at  least — the  creature  is  saved  the  trouble  of  moving 
them.  But,  pray,  how  are  they  used  ? 

Dr.  B. — They  are  situated  on  opposite  sides  of  the 
stomach  near  its  lower  end  where  it  begins  to  grow  nar- 
row, and  being  moved  up  and  down  by  the  action  of  this 
organ,  they  thoroughly  grind  up  the  food  which  passes 
between  them. 

In  the  Zoophytes  where  the  whole  internal  parts  of 
the  animal  constitute  the  digestive  cavity,  there  is  no 
distinction  of  the  process  into  chymification,  chy  lification, 
&,c.  but  it  is  all  performed  without  any  distinct  stages, 
and  the  chyle  instead  of  being  taken  up  by  a  particular 
set  of  vessels,  transudes  through  the  sides  of  this  cavity 
and  bathes  the  whole  body.  Some  of  the  medusae  instead 
of  a  single  mouth,  are  furnished  with  numerous  branch- 
ed feelers,  each  perforated  by  a  small  opening.  Each 
opening  leads  into  a  small  canal  which  joins  a  neigh- 
boring one,  and  so  on  till  four  large  trunks  are  formed 
which  end  in  the  stomach  and  convey  to  it  the  matters 
absorbed  by  the  apertures  of  the  feelers.  The  number 
of  the  latter  is  sometimes  eight  hundred. 


DIGESTION    OF    ZOOPHYTES*  71 

Emily. — This  is  a  very  close  approximation  to  the 
mode  of  nourishment  in  vegetables,  for  these  feelers 
seem  to  act  very  much  like  the  roots  of  plants. 

Dr.  B. — The  economy  of  the  Zoophytes  evidently 
manifests  an  approximation  to  that  of  vegetables.  Those 
sea-anemones  which  are  in  the  form  of  a  ray,  the  whole 
interior  surface  constituting  the  digestive  apparatus,  may 
be  turned  inside  out,  and  the  food  digested  just  as  well 
as  before  by  the  external  surface.  Some  plants,  you 
know,  may  be  planted  with  their  branches  in  the  soil  and 
their  roots  in  the  air,  and  after  a  time,  the  former  will 
be  converted  into  true  roots,  and  the  latter  will  put  forth 
leaves  and  blossoms. 

We  have  now  terminated  the  history  of  digestion. 
Before  we  can  follow  the  nutritious  portions  of  our  food 
any  farther,  we  must  consider  the  function  of  circulation 
as  it  is  called,  and  the  organs  by  which  it  is  carried  on. 
But  we  have  already  greatly  exceeded  our  usual  time, 
and  must  defer  this  subject  till  to-morrow. 


72  BLOOD. 


CONVERSATION  IV. 


Circulation — the  Hood — connection  of  circulation  with 
respiration — blood-vessels — heart,  arteries,  veins-~- 
motion  of  the  heart — anastomosis  of  arteries — the 
pulse — influence  of  disease  on  the  pulse — the  lesser 
or  pulmonic,  greater  or  systemic  circulation — capil- 
lary system — inflammation — adhesion . 

Emily. — To  day  we  are  to  have  some  account  of  the 
circulation;  but  I  hope  you  will  first  favour  me  with  an 
.explanation  of  this  term.  I  cannot  conceive  what  this 
allusion  to  a  circle  can  mean. 

Dr.  B. — The  function  derives  its  name  from  the  cir- 
cumstance that  the  organs  are  joined  together  in  such  a 
way  that  there  is  properly  neither  beginning  nor  end ;  but  as 
it  regards  the  function  itself,  they  are  connected  in  a  com- 
plete circle.  Their  use  in  the  vital  economy  is  to  con- 
vey different  materials  from  one  part  of  the  system  to 
another ;  to  receive  the  chyle  from  the  thoracic  duct 
and  expose  it  to  the  action  of  the  respiratory  organs; 
to  take  up  particles  of  the  body  which  are  no  longer  fit- 
ted for  its  purposes,  and  carry  .  them  to  the  excretory 
vessels  to  be  thrown  out  of  the  system  ;  and  finally,  to 
repair  the  waste  of  the  organs  with  suitable  materials  of 
supply.  The  fluid  which  they  contain,  thus  made  up  of 
heterogeneous  materials,  is  called  the  blood,  and  is  found 
in  all  animals  that  possess  a  circulating  system,  though 


COAGULATION    OP    THE    BLOOD.  73 

under  different  appearances.  In  the  first  place  let  us 
examine  the  properties  of  the  blood,  and  then  we  will  look 
at  the  heart  and  vessels  by  which  it  is  circulated. 

The  most  remarkable  property  of  the  blood,  is  that 
of  its  coagulating  when  drawn  from  the  vessels.  This 
process  seems  to  be  independent  of  external  causes,  and 
has  never  been  satisfactorily  accounted  for  by  physiolo- 
gists. 

Emily. — May  it  not  be  because  it  is  at  rest,  instead 
of  being  in  a  state  of  constant  motion  as  it  is  in  the  body  ? 
Or  perhaps  it  is  a  kind  of  freezing  process,  produced  by 
its  exposure  to  a  less  degree  of  warmth  than  the  tem- 
perature of  the  body. 

Dr.  B. — By  exercising  your  ingenuity  in  this  way, 
you  might  fabricate  many  other  theories,  all  which  have 
been  already  anticipated,  and  all  equally  incapable  of 
explaining  the  effect  in  question.  The  coagulation  of 
the  blood  is  not  prevented  by  keeping  it  constantly  agi- 
tated after  it  is  drawn,  and  is  rather  hastened  than  re- 
tarded, by  exposing  it  to  a  degree  of  heat  less  than  that 
of  the  body.  The  celebrated  John  Hunter  thought  he 
explained  it,  by  saying  that  the  blood  possessed  life,  and 
that  coagulation  was-  a  vital  process.  As  it  is  a  process 
of  a  very  peculiar  nature  and  one  of  great  use  in  the 
animal  economy,  it  may  not  be  improper  to  give  it  that 
name  ;  but  it  is  very  probable  that  the  causes  on  which 
it  depends  are  of  a  physical  nature.  It  is  a  little  re- 
markable that  in  animals  which  have  been  run  to  death, 
or  killed  by  lightning,  the  blood  loses  entirely  its  power 
of  coagulaticn. 

Emily. — These  are  the  same  conditions  under  which 
the  muscles  lose  their  contractilility  after  death.  May 
not  the  cause  be  the  same  in  both  ?  The  coincidence  is 
too  singular  to  be  accidental. 

Dr.  B. — It  is  very  probably  as  you  suggest,  but  the 

cause  whatever  it  may  be,  is  thereby  no  better  made 

known.     If  you  have  ever  observed  a  quantity  of  blood, 

an  hour  or  two  after  it  has  been  drawn,  and  suffered  to 

.    7 


74  ANALYSIS  OF  THE  BLOOD. 

remain  at  rest,  you  have  found  it  separated  into  three 
very  distinct  portions,  viz.  the  serum,  a  thin,  watery  fluid  ; 
the  fibrine,  a  thick,  tenacious,  jelly-like  mass  floating  on 
the  surface  of  the  serum  ;  and  a  quantity  of  red  globules 
which  adhere  to  the  under  surface  of  the  mass  of  fibrine. 

Emily. — I  recollect  having  observed  some  blood  a 
short  time  after  it  was  drawn,  and  was  surprised  to  find 
that  it  had  completely  lost  its  fine  dark  red  tint,  and  be- 
came almost  colorless.  I  suppose  that  if  I  had  raised 
the  cake  of  fibrine,  I  should  have  found  the  red  parts, 
which  had  so  mysterously  disappeared.  But  what  is 
the  composition  of  these  different  portions  ? 

Dr.  B. — The  constituent  prinicples  of  the  serum,  are 
water,  albumen  and  a  small  quantity  of  soda  ;  those  of 
the  fibrine,  we  fibrine,  a  peculiar  animal  substance,  and 
a  small  portion  of  a  few  saline  and  animal  substances  ; 
the  red  portion  of  the  blood  is  thought  to  resemble  fibrine 
and  contains  also,  iron  and  sulphur,  in  very  small  quan- 
tities. 

Emily.-— This  is  wonderful  indeed.  I  cannot  imag- 
ine in  what  manner  iron  and  sulphur  can  get  into  the 
blood,  for  we  certainly  take  neither  of  these  substances 
with  our  food. 

Dr.  B. — It  is  so  difficult  to  account  for  their  uniform 
appearance,  that  it  has  been  supposed  the  iron  was  form- 
ed in  the  process  of  analysis.  Their  aggregate  quantity 
in  an  individual  has  never  been  determined  with  much 
accuracy.  By  one  or  two  experiments  it  has  been  es- 
timated at  three  ounces,  the  whole  quantity  of  blood  be- 
ing abont  twenty  four  pounds. — Another  curious  fact  in 
regard  to  the  blood,  is  that  it  is  composed  of  minute  glob- 
ules similar  to  those  which  form  the  elementary  tissues. 

J2mily. — Is  the  blood  of  the  inferior  animals  like  that 
of  man  ? 

Dr.  B. — Chemical  analysis  detects  no  difference, 
though  some  difference  no  doubt,  exists.  It  has  been 
found  that  a  dog  may  be  bled  till  all  sensible  manifesta- 
tions of  life  have  disappeared,  and  restored  immediately 


USE  OF  THE  VESSELS.  75 

to  perfect  health  by  injecting  into  its  veins  the  blood  of 
another  dog,  while  that  of  a  man  or  horse  would  be  fol- 
lowed by  little  or  no  benefit.  On  the  whole,  the  blood 
may  be  considered  as  the  most  important  of  the  animal 
fluids,  being  the  grand  source  whence  the  system  re- 
ceives the  needful  supplies  to  repair  its  waste  and  main- 
tain its  growth. 

In  all  animals  that  possess  a  circulating  system,  we 
find  at  the  same  time,  an  apparatus  for  the  function  of 
respiration,  and  the  quantity ',  or  degree  of  perfection  of 
one.  of  these  systems  is  in  direct  proportion  to  that  of  the 
other.  As  the  blood  in  its  passage  through  the  body 
loses  much  of  its  nurient  materials,  and  acquires  others 
that  are  no  longer  fitted  for  the  purposes  of  life,  some 
provision  is  evidently  required  by  means  of  which  it  may 
throw  off  these  useless  portions,  and  receive  continual 
renovation. 

Emily. — And  this  provision  is  furnished  by  the  lungs. 
I  have  now  a  more  definite  idea  of  the  use  of  these  or- 
gans and  their  connection  with  the  circulation,  than  I 
ever  possessed  before.  I  begin  now  also,  to  perceive 
this  beautiful  system  of  harmony  of  action  and  mutual 
dependence,  which  associates  the  various  organs  of  the 
body  in  one  great  and  perfect  whole. 

Dr.  B. — You  now  readily  see  the  necessity  of  the 
blood's  being  constantly  submitted  to  the  action  of  the 
respiratory  organs,  and  as  constantly  changed  by  this 
action.  Every  portion  of  blood  before  being  sent  to  the 
body  must  be  carried  to  them,  and  the  essential  use  of 
the  circulating  vessels,  considered  in  their  simplest  con- 
dition, is  to  convey  the  blood  from  every  part  of  the  sys- 
tem to  the  lungs,  and  thence  back  to  the  system  again. 
Here  then  is  a  perfect  circle  of  action  which  is  inces- 
santly going  on  from  the  beginning  to  the  end  of  exis- 
tence. 

Emily. — What  a  multitude  of  vessels  must  be  requir- 
ed thus  to  carry  the  blood  to  and  from  every  and  the 


76  RELATIONS    OF    THE    VESSELS. 

minutest  portion  of  the  body  !     I  am  quite  impatient  to 
know  more  of  these  curious  organs. 

Dr.  B. — The  blood  vessels  are  strong  membranous 
tubes  composed  of  three  coats.  The  external  is  formed 
of  cellular  substance  ;  the  middle  of  muscular ;  and  the 
internal  is  one  of  a  peculiar  nature,  possessing  considera- 
ble elasticity  and  power  of  dilatation.  In  their  course 
they  are  constantly  subdividing  and  giving  off  branches, 
until  from  being  larger  than  a  man's  thumb  at  their  main 
trunk,  they  become  at  their  extremities  of  a  size  almost 
imperceptible.  They  are  distinguished  into  two  kinds ; 
one  conveying  the  blood  from  the  lungs  to  every  part  of 
the  body,  called  arteries  ;  the  other,  conveying  the  blood 
from  every  part  of  the  body  to  the  lungs,  called  veins. 
Each  of  these  sets  of  vessels  may  be  compared,  in  their 
disposition,  to  two  trees  united  by  their  trunks,  the  branch- 
es of  one  originating  in  the  lungs,  the  other  in  every  part 
of  the  body.  In  order  that  you  may  have  a  perfectly 
distinct  idea  of  the  relative  situation  of  these  vessels,  I 
have  prepared  this  diagram*  in  which  the  dotted  lines 
represent  the  arteries,  and  the  others  the  veins.  You 
see  the  branches  of  the  arteries  originating  in  L  the  lungs> 
running  together  till  at  last  they  form  one  larger  trunk, 
and  again  branching  off  to  terminate  in  B,  or  every  part 
of  the  body.  The  veins  originate  where  the  arteries. 


terminate,  run  together  and  form  one  larger  trunk,  branch 
off  again,  and  finally  extend  their  minute  ramifications 
to  every  part  of  the  lungs.  This  now,  constitutes  all  that 

*The  reader  must  bear  in  mind  the  distinction  between  a  plate  and 
a  diagram.  The  former  is  a  representation  of  the  actual  appearance  of 
an  object ;  the  purpose  of  the  latter  is  merely  to  illustrate  some  par- 
ticular principle,  or  manner  in  which  an  object  acts,  without  adhering 
at  all  to  the  exact  form  or  appearance  of  the  object. 


THB  HEART. 

is  necessary  to  the  simplest  form  of  the  circulation — a  set 
of  vessels  to  carry  the  blood  to  the  lungs,  and  another  to 
distribute  it  to  the  body. 

Emily. — Thus  far,  I  believe,  I  understand  the  matter 
perfectly  well,  but  I  cannot  conceive  by  what  means  the 
blood  is  moved  through  the  vessels  ;  unless  that  it  be  by 
the  action  of  the  vessels  themselves,  and  yet  I  have  al- 
ways supposed  that  the  heart  was  connected  in  some  way 
with  the  motion  of  the  blood,  but  you  have  not  spoken 
of  it. 

Dr.  B. — I  have  purposely  avoided  speaking  of  it,  in 
order  that  your  notions  of  its  relation  to  the  circulation 
might  not  be  confused  by  introducing  it  before  you  were 
properly  prepared  to  understand  it.  Have  patience 
one  moment  and  you  shall  understand  all.  In  this  dia- 
gram the  blood  is  supposed  to  be  moved  soly  by  the 
power  of  the  vessels  themselves ;  no  other  is  present  to 
assist  them.  Now,  in  some  of  the  lower  orders  of  ani- 
mals, this  is  precisely  the  manner  of  the  circulation — the 
power  of  the  vessels  without  any  other  aid,  is  snfficient 
to  propel  the  blood  through  them.  But  if  we  ascend 
the  scale  of  being  to  where  the  organization  has  increas- 
ed in  complexity  and  perfection — where  the  vital  ener- 
gies possess  more  activity  and  strength — where  conse- 
quently, a  greater  degree  of  action  is  required  in  the  ap- 
paratus which  is  to  support  the  vital  energies  and  repair 
their  losses,  we  find  an  additional  force  is  provided  to 
assist  the  action  of  the  vessels.  Now  then,  you  proba- 
bly can  tell  what  this  force  is. 

Emily. — I  presume  it  must  be  the  heart,  if  this  organ 
is  concerned  in  the  motion  of  the  blood,  for  I  cannot  see 
what  other  nse  it  can  have. 

Dr.  B. — You  are  right ;  and  since  you  have  com- 
prehended the  subject  so  well  thus  far,  you  will  perhaps 
perceive  at  once  in  what  part  of  the  circle  the  heart, 
should  be  placed,  in  order  that  it  may  act  with  the  great- 
est advantage. 

Emily. — Undoubtedly  it  would   be  where  the   two 


78  POSITITION    OF    THE    HEART, 

trunks  are  united  together.  .But  still,  I  have  no  idea 
how  the  heart  is  formed  so  as  to  be  made  a  moving  pow- 
er, nor  whence  it  derives  its  power. 

Dr.  B. — The  clearest  idea  that  we  can  have  of  the 
nature  and  purposes  of  the  heart,  is  by  considering  it  as 
it  exists  in  its  simplest  condition  in  the  inferior  aniftials^ 
merely  as  a  hollow  muscle  placed  somewhere  in  the  cir- 
cle, through  which  the  blood  passes  and  receives  from  its 
impulse  an  increased  rapidity  of  motion. 

Emily. — I  had  forgotten  to  ask  whether  it  was  in  the 
trunks  of  the  veins  or  arteries  that  the  heart  is  placed. 

Dr.  B. — A  question  well  asked,  for  the  position  of  the 
heart  in  respect  to  the  other  parts  of  the  circulating  sys- 
tem would  not  be  a  matter  of  indifference.  The  truth  is 
that  the  heart  considered  merely  as  a  moving  power,  may 
be  placed  either  where  the  venous,  or  the  arterial  trunks 
join.  In  the  former  case,  the  blood  will  be  driven  with 
increased  impetus  towards  the  respiratory  organs,  but  its 
motion  in  the  arteries  will  be  unaffected  by  it.  In  the 
latter  case,  the  blood  will  be  propelled  with  accelerated 
force  towards  every  part  of  the  body,  while  its  progress 
in  the  veins  remains  unaffected.  Instances  of  the  heart 
in  each  of  these  two  different  positions  may  be  found  in, 
the  inferior  animals— in  fishes,  of  the  first  position  ;  in  some 
of  the  shell  fish,  of  the  last.  Now  there  is  nothing  neces- 
sarily to  prevent  there  being  a  heart  in  each  of  these 
situations,  and  thereby  the  progress  of  the  blood  be  ac- 
celerated in  both  directions.  Such  is  actually  the  case  in 
some  of  the  molluscous  tribes,  as  the  cuttlefish  and  nau- 
tilus. Here  is  a  diagram  illustrating  this  form  of  the 
circulation.  If  now  we  consider  these 
two  hearts  brought  together  and  join- 
ed by  their  sides,  their  cavities  still  re- 
maining distinct,  we  shall  have  the 
heart  as  it  exists  in  man,  quadrupeds, 
birds  and  some  reptiles.  It  is  there- 
fore far  from  being  a  single  heart,  but 
is  strictlv  a  double  heart — two  single  hearts  united  together . 


STRUCTURE    OF    THE    HEART.  79 

.— Few  people,  I  suspect,  imagine  that  they 
have,  to  all  intents  and  purposes,  a  couple  of  hearts. 

j)r.  B. — If  we  were  to  judge  by  the  frequency  with 
which  they  lose  them,  they  ought  to  have  a  score.  Let 
me  now  call  your  attention  to  the  human  heart. 

The  double  heart  of  man  is  situated  in  the  lower  and 
front  part  of  the  chest  and  a  little  to  the  left  side.  It  is 
of  an  irregular,  pyramidal  shape,  with  its  base  upwards 
and  its  apex  pointing  obliquely  downwards,  and  is  en- 
closed in  a  membranous  bag  called  the  pericardium, 
which  fixes  it  in  its  place,  and  protects  it  from  the  con- 
tact of  other  organs.  Being  double  it  is  generally  dis- 
tinguished into  the  left  and  right  hearts,  or,  to  use  names 
which  at  the  same  time  give  an  idea  of  the  relative 
office  of  these  parts,  arterial  and  venous  hearts.  Neither  of 
these  hearts  is  formed  by  a  single  cavity,  but  each  is  com- 
posed of  two  cavities.  The  larger  is  called  the  ven- 
triele  ;  the  smaller  is  merely  an  appendage  to  the  other, 
and  is  called  the  auricle.  The  walls  of  the  ventricle 
are  exceedingly  thick  and  strong.  Their  internal  sur- 
face is  very  irregular,  owing  to  numerous  little,  fleshy 
columns,  which  run  in  the  direction  of  the  length  of  the 
ventricle,  in  bass  releif.  They  are  endowed  with  great 
contractile  power,  and  act  with  immense  force  in  bring- 
ing together  the  sides  of  the  ventricle.  Each  ventricle 
presents  two  apertures — one  by  which  the  blood  is  ad- 
mitted into  it,  and  the  other  by  which  it  is  sent  out. 
The  auricle  is  much  smaller  than  the  ventricle,  the  sides 
are  thinner,  and  its  fleshy  columns  are  less  powerful. — 
Now,  we  will  follow  the  blood  in  its  course  through  the 
hearts,  and  you  will  see  some  curious  contrivances  by 
means  of  which  they  exert  a  force  on  the  motion  of  the 
blood. 

First,  let  us  trace  it  through  the  venous  heart.  The 
venous  blood,  after  being  brought  from  every  portion  of 
the  body,  is  at  last  collected  into  two  great  veins,  the 
one  ascending  through  the  abdomen  with  the  blood  of 
the  lower  parts  of  the  body,  called  the  vena  cava  inferi- 


BO  VALVES    OF    THE    HEART. 

or;  the  other  descending  with  the  blood  of  the  head, 
chest,  and  upper  extremities,  called  the  vena  cava  supe- 
rior. The  two  veins  discharge  their  contents  by  a  com- 
mon opening  into  the  right  auricle.  This  cavity  being 
excited  by  the  presence  of  the  blood  which  completely 
fills  it,  contracts  suddenly  and  strongly  upon  the  mass 
within.  Being  pressed  in  all  directions  it  will  escape 
wherever  it  can  find  an  outlet.  Now  there  are  but  two 
openings  into  the  auricle — the  one  by  which  the  blood 
gained  admittance,  and  the  other  leading  into  the  ven- 
tricle. Through  the  former  it  is  impossible  for  it  to 
escape,  except  in  very  small  quantities,  because  a  long 
column  of  blood  is  in  these  veins,  presenting  too  great  a 
resistance  to  its  escape  in  that  direction.  The  latter 
opening — that  into  the  ventricle,  is  now  the  only  one 
left,  and  this,  as  soon  as  the  auricle  begins  to  dilate,  pre- 
sents a  free  and  open  passage  into  the  ventricle. 

Emily. — But  why  does  not  the  blood  flow  directly 
through  this  opening  while  the  auricle  is  filling  ?  I  see 
nothing  now,  to  prevent  it. 

Dr.  B. — You  will  see  in  a  moment  why  it  does  not ; 
but  first  we  must  trace  it  into  the  ventricle.  This  cavi- 
ty when  filled,  like  the  auricle  contracts  upon  the  blood, 
which  must  find  an  outlet  either  back  through  the  open- 
ing into  the  auricle,  or  into  the  vessel  which  carries  it  to 
the  lungs,  called  the  pulmonary  artery.  A  very  in- 
genious though  simple  contrivance  effectually  prevents 
it  from  passing  back  again  into  the  auricle.  From  every 
part  of  the  circular  opening  between  these  two  cavities, 
arises  a  thin,  light  membrane  cleft  almost  down  to  its 
roots,  in  three  places,  thus  dividing  it  into  three  sepa- 
rate pieces.  These  pieces  are  still  farther  divided,  giv- 
ing the  membrane  a  fringe-like  appearance.  These 
fringes  are  connected  to  the  walls  of  the  ventricle  by 
many  little  tendinous  strings  sufficiently  long  to  allow 
the  fringes  a  considerable  extent  of  motion.  Now 
when  the  ventricle  contracts,  the  blood  driven  in  all  di- 
rections insinuates  itself  behind  these  fringes,,  and  raise? 


THE    PULMONARY    ARTERY.  81 

them  up  as  far  as  their  tendinous  strings  will  permit. 
This  is  sufficiently  far  for  all  the  fringes  to  meet  one 
another,  and  thus  form  a  perfectly  impervious  mem- 
brane stretching  across  the  opening.  When  the  ventri- 
cle dilates,  the  fringes  are  pulled  down  by  the  separa- 
tion of  the  walls  to  which  they  are  tied,  and  they  hang 
loose  in  the  ventricle  till  they  are  again  raised  by  its 
contraction.  Thus,  you  observe,  they  act  the  parts  of 
valves,  and  are  called,  tricuspid  valves,  from  the  pointed 
appearance  of  the  three  main  pieces. 

Emily. — Ah,  now  I  perceive  why  the  blood  which 
fills  the  auricle  does  not  run  directly  through  it  into  the 
ventricle.  While  the  auricle  is  filling,  the  ventricle  is 
contracted  and  expelling  its  contents,  so  that  the  same 
valves  which  prevent  the  blood  from  escaping  into  the 
auricle,  also  prevent  it  from  escaping  into  the  ventricle 
before  the  auricle  is  filled.  Is  not  this  correct  ? 

Dr.  B. — Yes ;  and  now  having  a  clear  idea  of  it  thus 
far,  you  will  comprehend  the  rest  with  very  little  diffi- 
culty. The  blood  has  now  been  pushed  into  the  pul- 
monary artery,  but  some  contrivance  is  obviously  re- 
quired to  prevent  the  blood  from  passing  back  again  into 
the  ventricle  while  it  is  dilating.  This  object  is  also 
effected  by  valves.  Just  at  the  mouth  of  the  artery,  are 
three  thin,  strong  membranes  of  a  semi-lunar  shape, 
with  their  loose  edges  hanging  free  in  the  cavity  of  the 
artery.  The  blood  in  the  artery  pressing  in  all  direc- 
tions, raises  these  valves  till  their  sides  are  brought  to- 
gether, and  thus  the  cavity  of  the  artery  is  completely 
closed  up.  Being  prevented  from  passing  in  this  direc- 
tion, it  flows  on  through  the  pulmonary  artery,  and  is 
finally  distributed  to  every  portion  of  the  lungs. 

Emily. — I  cannot  see  with  what  propriety  you  call 
this  vessel  an  artery,  for  it  certainly  conveys  venous 
blood. 

Dr.  B. — It  carries  venous  blood,  indeed,  but  it  has 
the  structure  of  the  arteries,  and  its  course  is  from,  not 
to,  the  heart.  For  the  same  reason,  the  vessels  which 


82  BLUE    BOYS. 

collect  the  blood  from  the  lungs  and  transmit  it  to  the 
heart,  are  called  veins  instead  of  arteries.  Having  now 
been  submitted  to  the  action  of  the  lungs,  it  is  taken  up 
by  a  multitude  of  minute  vessels,  which  are  continually 
joining  one  another  in  their  course,  till  they  finally  form 
four  large  trunks,  called  the  pulmonary  veins.  They 
come  two  from  each  side,  and  enter  at  opposite  sides  of 
the  arterial  auricle.  Thence  the  blood  is  transmitted  to 
the  arterial  ventricle,  the  opening  between  which  and  the 
auricle,  is  provided  with  a  valve,  whereof  the  construc- 
tion and  use  are  very  similar  to  those  in  the  venous  heart. 
The  valve  here,  however,  is  only  twice  cleft,  and  from  a 
fancied  resemblance  to  a  mitre,  is  called  the  mitral  valve. 
The  arterial  ventricle  is  longer,  stronger  and  thicker, 
than  the  other,  but  in  all  other  respects,  it  closely  re- 
sembles it.  The  contraction  of  the  arterial  ventricle 
forces  the  blood  into  the  aorta,  the  grand  trunk  of  the 
arterial  system.  This  vessel  is  also  furnished  with  semi- 
lunar  valves,  in  the  same  manner  as  the  pulmonary  ar- 
tery. The  venous  auricle  and  ventricle  are  more  capa- 
cious, but  possess  less  power  of  contraction,  than  those 
of  the  other  side,  for  having  to  send  the  blood  only  to 
the  lungs,  which  are  but  a  short  distance  from  them,  an 
equal  degree  of  force  with  that  exerted  by  the  others 
which  throw  it  over  the  whole  body,  is  obviously  not 
required.  This  completes  our  account  of  the  heart,  and 
the  course  of  the  blood  through  its  different  cavities. 

Emily. — Before  we  leave  this  part  of  the  subject, 
please  to  enlighten  me  on  one  point  about  which  I  am 
uncertain.  The  cavities  of  the  two  hearts,  you  observed, 
were  perfectly  distinct — without  the  slightest  communi- 
cation. Now,  though  I  do  not  doubt  the  fact,  I  am  at  a 
loss  to  see  the  reason  of  it. 

Dr.  B. — If  you  were  fully  acquainted  with  the  na- 
ture of  respiration,  you  could  not  be  at  a  loss  one  mo- 
ment, to  perceive  what  mischievous  effects  such  a  com- 
munication would  produce.  Venous  blood,  you  know, 
would  be  mixed  with  arterial,  and  blood  which  has  not 


INCESSANT  ACTION  OF  THE  HEART.  83 

been'  subjected  to  the  action  of  the  lungs,  and  conse- 
quently unfit  for  nutrition,  would  get  into  the  arteries, 
and  be  distributed  to  the  body.  Sometimes,  such  a 
communication  does  exist  from  birth,  and  from  the  pe- 
culiar appearance  of  the  subjects  in  which  it  takes  place, 
they  are  called  blue  boys.  They  seldom  survive  long  ; 
most  of  them  dying  in  a  few  hours,  though  some  have 
lived  two,  three,  and  even  seven,  or  eight  years.  The 
effects  of  such  a  communication  were  strikingly  illus- 
trated in  a  patient  who  died  a  few  years  ago  in  one  of 
the  Parisian  hospitals,  in  whom  it  had  been  produced  by 
a  disease  of-  the  heart.  At  this  time  he  was  forty-one 
years  of  age.  His  face  was  remarkably  livid,  the  vessels 
were  injected  with  blood,  his  lips  were  unusually  large, 
and  like  the  rest  of  his  body,  were  of  a  deep  blue  color. 
His  respiration  was  laborious,  his  pulse  extremely  irreg- 
ular, and  he  was  unable  to  articulate  two  words  in  suc- 
cession, without  stopping  to  take  breath.  He  was  obliged 
to  sleep  in  a  sitting  posture,  and  was  particularly  remark- 
able for  his  indolence.  This  indolence,  joined  to  great 
natural  simplicity,  was  such  that  he  could  not  do  without 
the  assistance  of  his  wife.  He  finally  died  from  suffo- 
cation. The  lividity  was  occasioned  by  the  dark  venous 
blood  that  had  entered  the  arteries,  and  which,  unable  to 
afford  the  necessary  stimulus  to  the  powers  of  life,  pro- 
duced his  uncommon  indolence.  j 

Emily. — The  action  of  the  heart  is  incessant,  is  it  not, 
enjoying  no  moments  of  repose  or  relaxation  of  duty, 
like  some  of  the  other  organs  ?  The  mischief  that  would 
follow  an  entire  cessation  of  its  action,  is  very  obvious, 
but  I  do  not  understand  why  such  an  arrangement  was 
necessary. 

Dr.  B. — Or  in  plainer  language,  why  is  the  body  made 
—just  as  it  is  made  ?  This  is  the  legitimate  extent  of  your 
question  when  carried  out.  Now,  that  the  body  might 
have  been  so  constructed  as  that  the  circulating  system 
should  have  had  its  periods  of  repose,  is  perhaps  possible. 
That  it  might  have  been  constructed  without  any  circu- 


84  SOURCE    OF    THE    HEART*S     POWER. 

lation  at  all,  if  the  Great  Architect  had  so  pleased,  is  also 
possible.  But  all  this  is  none  of  our  business.  We  are 
to  take  the  animal  economy  as  we  find  it,  and  rest  satis- 
fied with  the  beauty  and  wonder  which  we  observe. 
That  the  constant  action  of  the  heart  is  necessary,  is 
certain  ;  how  it  is  so  constituted  as  to  commence  its  la- 
bours with  the  first  visible  signs  of  organization,  and  fin- 
ish them  only  with  the  last  moments  of  existence,  with- 
out causing  a  feeling  of  fatigue,  is  a  question  not  so  easily 
answered  ;  but  the  fact  is  no  more  wonderful,  than  that 
the  stomach  should  act  without  giving  the  sense  of  fatigue. 

Emily. — But  does  not  the  action  of  the  heart  cease 
during  fainting  ?  Such  is  my  impression,  and  if  the  fact 
be  true,  I  see  not  how  to  reconcile  it  with  what  you  have 
said  in  regard  to  the  disasterous  consequences  which 
such  an  accident  would  produce. 

Dr.  B. — True  indeed,  its  action  may  cease  during 
fainting  fer  a  moment,  and  then  be  resumed  ;  but  it  is 
only  for  a  moment— if  the  interval  be  protracted,  the 
blood  coagulates  in  the  vessels,  and  its  motion  is  thus 
effectually  prevented. 

Emily.— How  then  do  those  persons  ever  recover, 
who  for  three  or  four  days,  have  lain  in  a  trance  as  it  is 
called,  and  apparently  dead,  for  the  least  sign  of  life 
cannot  be  perceived  ? 

Dr.  B. — They  were  not  in  fact  dead  ;  neither  does 
the  heart,  in  such  cases,  entirely  cease,  though  its  ac- 
tion is  so  feeble,  that  unless  it  be  closely  examined,  it 
will  escape  our  notice,  as  has  been  the  case  in  all  these 
instances. 

Emily. — Still,  there  does  appear  something  very  sin- 
gular about  the  action  of  the  heart — something  altogeth- 
er different  from  that  of  other  organs.  Pray,  Dr.  B., 
whence  does  it  derive  the  power  which  imparts  such 
astonishing  constancy  and  accuracy  to  its  motions. 
This  is  inexplicable  to  me. 

Dr.  B. — Not  only  to  you,  but  to  physiologists,  from 
the  earliest  times,  to  whom  it  has  always  been  a  cause 


of  much  wonder  and  doubt,  and  as  might  have  been 
expected,  has  elicited  much  wild  and  visionary  specula- 
tion. The  ancients  thought  there  was  an  innate  fire  in 
the  heart,  which  produced  its  motion,  and  a  chemical 
sect  attributed  it  to  an  effervescence  in  the  heart,  caused 
by  the  mixture  of  different  kinds  of  blood.  You  smile 
at  such  absurdities,  but  they  can  teach  you  an  all-impor- 
tant truth,  which  cannot  be  too  strictly  adhered  to — never 
to  reason  on  scientific  subjects,  without  having  first  care- 
fully considered  all  the  facts  connected  with  the  case  in 
question,  and  then  deducing  cautiously  the  general  prin- 
ciples that  arise  from  them.  This  is  the  basis  of  all  true- 
philosophy.  The  most  that  we  know  of  the  motions  of 
the  heart  is,  that  they  are  under  the  influence  of  the 
nervous  system  in  a  very  great  degree,  and  particularly 
of  that  portion  of  it  which  is  connected  with  the  spinal 
marrow. 

Emily. — What  ground  is  there  for  even  this  fact  ? 

Dr.  B. — In  the  first  place,  it  is  inferred  from  the  fact, 
that  animals  have  been  born  without  a  brain,  in  which 
the  heart  and  the  rest  of  the  body  were  perfectly  well 
formed, — a  proof  that  the  heart  derives  its  nervous  power 
from  the  spinal  marrow,  and  not  the  brain.  Secondly, 
it  is  inferred  from  the  experiments  of  Le  Gallois,  who 
ascertained  that  though  a  creature's  head  were  cut  off,  yet 
if  the  bleeding  vessels  were  tied  up,  and  artificial  respi- 
ration maintained  by  blowing  air  into  the  wind-pipe  from 
a  pair  of  bellows,  the  heart  would  nevertheless  continue 
to  act  for  a  considerable  time  after  the  decapitation  of 
the  animal.  This  is  about  the  sum  and  substance  of  all 
we  know  concerning  the  source  of  the  heart's  power. 

Emily. — As  the  blood  is  incessantly  revolving  in  a 
circle,  it  must  be  continually  returning  at  certain  periods 
to  the  place  whence  it  started.  Now,  I  am  desirous  to 
know  how  long  a  time  is  required  for  a  given  quantity  of 
blood  to  complete  the  revolution. 

Dr.  B. — If  you  suppose  that  the  arterial  ventricle  con- 
tracts seventy-five  times  in  a  minute,  expelling  two  ounces, 
8 


86  FIRST    APPEARANCE    OF    THE    HEART. 

Troy  weight,  at  each  contraction,  and  the  whole  quantity 
of  biood  in  the  vessels  to  be  thirty-three  pounds,  you  will 
have  no  difficulty  in  answering  the  question  yourself. 

Emily. — One  hundred  and  fifty  ounces,  or  twelve  and 
a  half  pounds,  will  be  expelled  from  the  heart  each  mi- 
nute, consequently  thirty-three  pounds  in  two  minutes 
and  thirty-six  seconds,  so  that  the  whole  mass  of  the 
blood  will  go  the  round  of  the  circulation  twenty-three 
times  in  an  hour.  What  astonishing  rapidity  ! 

How  wonderful  that  in  so  small  a  space  of  time,  every 
portion  of  blood  sent  out  from  the  heart  goes  to  the  body, 
thence  to  the  lungs,  and  finally  back  to  the  heart  again. 
And  with  what  astonishing  force  too  the  heart  must  act 
to  propel  so  large  a  mass ! 

Dr.  B. — This  great  power  has  always  excited  the  at- 
tention of  physiologists,  and  at  a  time  when  mathematical 
calculations  were  greatly  in  fashion  in  medical  science, 
many  attempts  were  made  to  ascertain  its  exact  quantity. 
One  philosopher  performed  a  great  many  experiments, 
and  w^ent  through  many  tedious  calculations  to  ascertain 
the  power  with  which  the  heart  expelled  the  blood,  and 
lo  the  result  !  He  found  it  equal  to  one  hundred  and 
eighty  thousand  pounds  !  Another,  after  going  over  a 
field  of  investigation  full  as  extensive,  came  to  the  con- 
clusion, that  it  was — five  ounces  and  a  half  1  Another 
estimated  it  at  fifty  pounds,  in  which  estimate  he  proba- 
bly came  nearer  to  the  truth  than  either  of  the  others. 

Being;  the  most  essential  of  all  the  organs,  the  heart  is 
the  first  one  formed  in  the  organization  of  the  higher  ani- 
mals. Jf  the  egg  of  a  bird  be  examined  in  the  first  peri- 
ods of  incubation,  the  heart  will  be  seen  a  hardly  per- 
ceptible speck,  having  already  begun  its  motions,  before 
the  rudiments  of  any  other  part  can  be  observed.  Many 
of  the  other  organs  are  sometimes  found  wanting,  but 
never  the  heart.  Here  it  is,  beating  on  untired  from 
the  beginning;  to  the  end  of  life.  This  finishes  our  ac- 
count of  the  circulation  through  the  heart. 

Emily. — Now,  I  suppose  we  are  to  trace  it  in  its  pro- 


DISTRIBUTION    OF    THE    ARTERIES. 

gress  to  the  various  parts  of  the  body,  as  it  is  carried 
along  by  the  arteries.  What  a  multitude  of  these  ves- 
sels there  must  be  ;  it  would  be  impossible  to  remember 
all  their  names. 

DTt  #. — And  we  can  see  but  a  small  portion  of  that 
system  of  vessels  which  transmit  their  contents  to  the  mi- 
nutest point  in  the  body,  insomuch  that  not  the  slightest 
scratch,  nor  prick  of  the  finest  needle  can  be  made, 
without  wounding  them,  and  producing  an  effusion  of 
blood.  The  aorta,  constituting  the  great  trunk  of  the 
arterial  system,  rising  up  from  the  arterial  ventricle, 
and  suddenly  bending  over,  passes  straight  down  the 
trunk  of  the  body  and  lies  near  the  spine.  From  its 
arch,  it  gives  off  several  large  vessels  which  go  to  the 
arms,  neck  and  head,  viz.  one  to  each  arm,  called  the 
subdaman  arteries,  and  four  to  the  neck,  face,  and  head, 
the  two  carotids,  and  two  vertebrals.  The  branches  sent 
off  by  these  vessels  supply  all  these  parts.  In  its  pas- 
sage down  the  trunk,  it  sends  branches  to  the  stomach, 
liver  and  spleen,  and  the  other  internal  organs.  In  the 
lower  part  of  the  abdomen,  it  divides  into  two,  called  the 
iliac  arteries,  which  supply  the  neighboring  organs, 
and  the  inferior  extremities.  The  arterial  branches 
are  generally  given  off  at  acute  angles ;  sometimes 
however  at  right,  and  in  a  few  instances  at  obtuse  angles. 
The  branches  are  smaller  than  the  vessels  from  which 
they  are  given  off,  and  thus  the  vessels  go  on  decreasing 
in  size,  even  to  their  minutest  ramifications. 

Emily. — But  as  the  branches  taken  together  have  ob- 
viously a  greater  diameter  than  the  trunk  itself,  the  mo- 
tion of  the  blood  must  be  continually  grower  slowing,  ac- 
cording to  a  well  known  law  of  the  distribution  of  forces. 
The  zig  zag  direction  of  some  of  the  vessels,  and  the 
great  size  of  the  angles  at  which  they  are  given  off  must 
also  have  a  tendency  to  retard  its  motion.  But  I  have 
observed,  in  a  plate  of  the  arteries,  two  bending  to- 
wards each  other  and  at  last  forming  but  one  vessel ; 
others  are  connected  by  a  branch  running  between  them. 


88 


SITUATION    OF    THE    ARTERIES. 


The  former  sort  of  communications  must  accelerate  the 
motion  of  the  blood,  for  you  know  when  a  fluid  passes 
from  a  larger  into  a  smaller  channel,  the  forces  by  which 
it  is  impelled  remaining  the  same,  its  progress  is  quick- 
ened. 

Dr.  B. — These  arterial  communications  are  called 
anastomoses,  and  are  very  useful,  in  supplying  organs 
and  parts  from  which,  by  any  cause,  the  usual  supplies 
are  cut  off.  This  utility  is  very  manifest  in  diseases  of 
of  vessels  which  require  them  to  be  tied.  Thus  the  two 
great  arteries  which  go  up  along  the  sides  of  the  neck, 
meet  together  in  the  base  of  the  brain  and  form  a  single 
vessel,  so  that  if  one  of  these  vessels  be  tied,  the  brain, 
you  see,  will  be  supplied  with  blood  just  as  well  as  be- 
fore. 

Emily. — But  it  certainly  cannot  receive  so  much,  be- 
cause it  is  evident  that  one  vessel  cannot  transmit  so 
much  blood  as  two. 

Dr.  B. — This  difficulty  is  obviated  by  a  very  admira- 
ble law  of  the  human  economy.  When  an  artery  is  tied 
or  otherwise  obstructed,  the  neighboring  vessels  enlarge 
their  calibre,  so  that  they  ultimately  transmit  to  the  parts 
as  much  blood  as  they  received  before.  Such  is  this  sin- 
gular power  of  the  vessels  to  accommodate  their  capaci- 
ty to  the  wants  of  the  system,  that  modern  surgeons  have 
presumed  upon  it  to  an  almost  incredible  degree,  and 
with  such  beneficial  results  as  to  redound  greatly  to  the 
honour  of  their  art.  When  an  artery  is  diseased,  even 
though  it  be  the  chief  artery  in  the  limb,  they  do  not 
hesitate  to  tie  it  up,  to  prevent  it  from  bursting  hs  coats 
and  killing  the  patient  by  a  terrible  hemorrhage.  Sir 
Astley  Cooper  once  tied  up  the  aorta  itself  in  the  ab- 
domen just  before  it  divides  into  the  iliacs,  and  though 
his  patient  died  a  few  hours  afterwards,  he  attributed  his 
death  to  the  disease  rather  than  the  operation. 

The  position  of  the  arteries  evinces  that  great  precau- 
tion has  been  kept  in  view  for  their  security  and  protec- 
tion against  external  accidents,  They  generally  lie  deep 


MOTION  OF  THE  BLOOD  IN  THE  ARTERIES.    89 

seated  far  beneath  the  muscles,  and  close  to  the  bones, 
and  are  never  found  in  places  where  they  would  be  ex- 
posed to  injuries.  Thus,  no  large  arteries  are  found  on 
the  back  or  face  ;  those  of  the  chest  run  along  on  the  in- 
ner side  of  the  ribs,  and  those  of  the  legs  where  accidents 
are  frequently  occuring,  are  very  deeply  seated  near  the 
bones  and  are  difficult  of  access. 

Emily. — But,  Dr.  B.,  are  the  arteries  entirely  passive, 
as  it  respects  the  motion  of  the  blood  ?  As  the  heart, 
according  to  your  definition,  is  a  power  whose  object  is 
merely  to  assist  the  motion  of  the  blood,  I  still  presumed 
that  they  had  some  share  in  the  duty. 

Dr.  B. — The  motion  of  the  ulood  in  the  larger  ar- 
teries is  derived  entirely  from  the  impulse  of  the  heart, 
but  in  the  smaller  branches  it  is  chiefly  effected  by  the 
action  of  the  vessels  themselves.  It  may  be  stated  gen- 
erally, that  as  we  proceed  from  the  heart  we  find  its 
power  diminishing,  and  that  of  the  arteries  increasing, 
until  we  arrive  at  the  extremities  of  the  vessels  where 
the  force  of  the  heart  is  nothing.  Though  the  blood  is 
thrown  into  the  arteries  at  intervals,  yet  they  are  always 
full — the  cause  of  this,  I  suppose,  1  need  not  point  out 
to  you. 

Emily. — If  I  am  not  mistaken  it  is  because  a  column 
of  blood  being  displaced,  no  greater  than  that  which  en- 
ters the  vessels  at  each  contraction  of  the  ventricle,  they 
will  be  equally  full  during  both  the  contraction  and  dila- 
tion of  the  heart.  But  will  the  motion  of  the  blood  be 
uniform  ? 

Dr.  B. — Certainly  not,  for  during  the  dilatation  of  the 
heart,  its  progress  must  unavoidably  be  slackened,  and  if 
a  puncture  be  made  in  an  artery  the  blood  will  gush  out 
in  regularly  successive  jets.  If  the  motion  of  the  blood 
were  uniform,  it  would  flow  out  in  a  steady  stream.  This 
flowing  of  successive  waves  of  blood  may  be  easily  per- 
ceived by  placing  the  finger  over  an  artery,  and  pressing 
upon  it  with  sufficient  force  to  diminish  its  calibre  slight- 
ly. This  presents  an  obstacle  to  the  free  passage  of  the 
•  8* 


NUMBER    OF    PULSATIONS. 


blood,  and  the  finger  will  feel  it  very  distinctly  moving 
along.  Find  the  artery  which  runs  along  the  upper  side 
of  the  wrist  and  try  it  for  yourself,  —  there. 

Emily.  —  Why  this  is  the  pulse  which  I  have  felt  a 
thousand  times  before.  This  phenomenon,  then,  which 
has  always  appeared  so  mysterious  to  me,  is  nothing  but 
the  successive  waves  of  blood  impinging  against  the 
sides  of  the  artery  which  is  compressed  by  the  finger. 
As  the  whole  mass  of  the  blood  is  put  in  motion  at  each 
contraction  of  the  heart,  the  pulse  must  consequently  be 
felt  at  the  same  time  over  the  whole  body.  This  is  a 
new  fact  to  me  also.  Pray  tell  me,  Dr.  B.,  what  there 
is  about  the  pulse,  which  requires  physicians  to  feel  it,  at 
every  visit  they  make  their  patients  ?  Much  as  I  have 
learnt  about  this  subject,  this  still  has  an  air  of  mystery 
about  it  to  me. 

Dr.  B.  —  The  intimate  relations  and  nice  sympathies 
that  exist  between  the  heart  and  every  other  organ,  'are 
such,  that  the  slightest  derangement  in  any  of  them, 
generally  affects  the  action  of  the  heart.  Now  the  pulse 
is  the  index  of  the  power  and  number  of  the  heart's  con- 
tractions ;  of  the  quantity  of  blood  thrown  out  ;  and  con- 
sequently of  the  general  condition  of  the  system,  relative 
to  health  and  disease. 

Emily.  —  Ah,  this  clears  up  the  mystery,  and  accounts 
at  the  same  time,  I  suppose,  for  the  grave,  wise-looking 
face  which  the  doctor  puts  on  in  the  act  of  feeling  the 
pulse.  You  remarked  just  now,  that  the  heart  contracts 
seventy-five  times  in  a  minute  ;  is  this  the  exact 
uurnber  of  the  pulsations  in  a  state  of  health  ? 

Dr.  B.  —  This  varies  according  to  climate,  age,  sex, 
health,  &c.  The  common  standard  of  an  adult  male 
however,  in  good  health,  is  about  seventy  ;  but  owing  to 
difference  of  temperament,  habits  of  living,  &c.  it  gener- 
ally varies  from  sixty  to  eighty.  Dr.  Heberden  mentions 
a  person  whose  pulse  did  not  exceed  sixteen  ;  and  an 
old  writer  speaks  of  one,  whose  pulse  was  not  more  than 
ten  beats  in  a  minute.  At  birth,  it  is  as  many  as  one 


DIFFERENT  KINDS    OF    PULSE.  91 

hundred  and  forty ;  but  as  the  child  grows  older,  the  cir- 
culation slackens,  and  at  two  years  of  age,  it  has  become 
reduced  to  one  hundred.  At  twelve  or  fifteen,  it  is  about 
eighty,  and  in  old  men,  it  is  generally  below  sixty.  In 
women,  the  pulse  is  generally  ten  or  twelve  strokes 
quicker  than  in  men.  In  weakly  and  irritable  frames, 
the  pulse  is  considerably  above  the  common  standard. 
The  cheerful  passions  and  affections,  such  as  joy,  love, 
and  sudden  pleasure,  generally  accelerate  the  heart's  ac- 
tion, unless  carried  to  excess — then  it  seems  to  be  over- 
whelmed by  the  magnitude  of  the  feeling,  and  sometimes 
ceases  to  beat  forever.  The  depressing  affections,  such 
as  grief,  fear,  melancholy,  &c.  retard  its  action,  and  the 
sudden  news  of  some  unexpected  disaster,  has  arrested 
it  forever. 

Emily. — Does  the  presence  of  disease  in  the  body, 
vary  the  heart's  pulsation  in  regard  to  number  merely  ? 
If  you  will  allow  me  to  hazard  a  conjecture,  I  should 
think  that  the  force  and  quickness  of  the  heart's  con- 
tractions might  be  liable  to  variations  from  this  cause, 
and  thus  the  pulse  be  affected. 

Dr.  B. — You  are  perfectly  correct  in  your  conjec- 
ture ;  and  the  various  kinds  of  pulse  produced  in  this 
way,  have  received  appropriate  names  from  physicians. 
For  instance,  when  the  artery  appears  under  the  finger 
as  il  increased  in  calibre,  and  transmitting  a  greater  col- 
umn of  blood,  it  is  called  a  full  pulse;  the  opposite  is 
styled  the  small,  contracted  or  wiry  pulse,  the  artery 
feeling  as  if  it  was  contracted  to  the  size  of  a  thread,  or 
wire.  When  a  very  slight  presure  is  sufficient  to  prevent 
the  passage  of  the  blood  through  the  vessel,  the  pulse  is 
said  to  be  soft  ;  it  is  called  hard  on  the  contrary,  when 
the  artery  is  not  easily  compressed.  In  short,  the  pres- 
ence of  disease  in  the  body  varies  the  action  of  the  heart 
to  infinity. 

Emily. — The  heart  then  must  possess  very  numerous 
and  close  connexions  with  the  rest  of  the  system,  does  it 
not? 


92  MOTION    OF    THE    BLOOD    IN    THE  VEINS, 

Dr.  B. — Excepting  the  digestive  system,  no  organ 
possesses  such  close  and  extensive  sympathies,  as  the 
heart.  The  least  degree  of  constitutional  excitement 
is  propagated  to  the  heart,  and  is  manifested  in  a  modi- 
fication of  its  actions.  Thus  you  may  easily  conceive 
that  the  pulse  should  afford  to  the  physician  one  of  the 
surest  criterions  in  judging  of  the  nature  and  severity  of 
disease.  The  circulation  of  the  blood  was  discovered  in 
1620,  by  Harvey,  and  the  immense  advantages,  which 
this  discovery  has  given  to  modern  physicians,  are  of 
more  value  than  all  the  accumulated  discoveries  and  ob- 
servations of  all  his  predecessors. 

Emily. — Before  quitting  this  part  of  the  subject,  I  wish 
to  ask  a  question  which  1  have  been  expecting  all  along 
your  explanations  would  render  unnecessary.  I  want 
to  know  if  the  heart  is  the  seat  of  any  of  the  passions,  or 
moral  affections ;  we  hear  every  day  you  know,  of  a  good 
heart,  a  bad  heart,  a  kind  heart,  an  open  heart,  &c. 

Dr.  B. — Such  indeed  was  the  belief  of  the  ancients, 
and  also  of  one  or  two  modern  physiologists,  and  though 
the  notion  is  exploded  now,  yet  the  language  which  it 
gave  rise  to  is  still  retained.  It  originated  from  the  fact, 
that  in  violent  passions  the  heart  is  more  or  less  affected 
in  consequence  of  its  sympathy  with  the  brain.  The 
heart  does  not  seem  to  be  endowed  with  common  sensi- 
bility, for  Richerand  a  distinguished  French  surgeon,  in 
one  of  his  operations,  exposed  the  heart  and  touched  it 
with  the  handle  of  his  knife,  without  the  patient's  expe- 
riencing any  sensation  whatever. 

Emily. — So  far  then  as  the  seat  of  the  feeling  is  con- 
cerned, we  may  with  equal  propriety  say  of  a  person,  that 
he  has  agood,  or  a  kind  liver,  as  a  good  or  a  kind  heart. 
But  please  to  resume  your  account  of  the  circulation 
which  I  so  unceremoniously  interrupted. 

Dr.  B. — I  was  about  to  follow  the  blood  in  its  course 
through  the  veins  whose  office  it  is,  to  convey  it  to  the 
respiratory  organs.  The  veins  are  much  more  numer- 
ous than  the  arteries,  for  arteries  of  a  middle  size  are 


CAUSE  OF  THE  BLOOD*S  MOTION   IN  THE  VEINS.     93 

generally  accompanied  by  two  veins  ;  their  aggregate 
capacity  is  consequently  greater,  and  the  blood  which 
they  contain  bears  the  proportion  of  9  to  5,  to  that  in  the 
arteries.  Their  course  is  straighter  and  they  more  fre- 
quently anastomose  than  the  arteries.  The  larger  veins 
are  generally  enclosed  in  a  common  sheath  with  the  ar- 
tery that  is  going  to  the  part  whence  the  vein  has  come  ; 
the  smaller  veins  are  unaccompanied  by  arteries  and  are 
more  superficial  in  their  situation.  The  blood  brought 
from  all  parts  of  the  system,  is  collected,  as  we  have  be- 
fore observed,  into  two  great  trunks  which  pour  it  into 
the  venous  auricle  of  the  heart. 

As  the  circulation  has  now  been  described,  it  may 
naturally  be  divided  into  two  parts,  or  stages,  in  reference 
to  its  relation  with  the  heart,  viz.  from  the  heart,  through 
the  lungs,  back  to  the  heart ;  then  through  every  part  of 
the  body,  back  to  the  heart  again.  The  former  portion  of 
the  course  is  called  the  lesser,  (*r  pulmonary  circulation  ; 
the  latter,  the  greater,  or  systemic  circulation. 

Emily. — You  do  not  mean  certainly,  that  there  are 
two  complete  circles  described  by  the  course  of  the 
blood  ? 

Dr.  B. — No  ;  but  that  the  course  is  rather  represen- 
ted by  the  arcs  of  two  circles,  one  larger  than 
the  other,  connected  by  their  extremities,  in 
this  manner.  Here  you  see  that  from  which- 
ever ventricle  the  blood  is  sent  out,  it  does 
not  return  to  the  same  ventricle  till  it  has 
completed  the  whole  circulation,  both  great- 
er and  lesser. 

Emily. — I  do  not  understand  how  the  blood  is  moved 
in  the  veins  contrary  to  its  own  gravity,  as  it  is  in  some 
parts  of  the  body,  for  you  said  that  the  action  of  the 
heart  ceased  in  the  smaller  arteries. 

Dr.  B. — This  indeed  is  a  very  obscure  point  in  phy- 
siology, though  the  theories  that  have  been  made  to  ex- 
plain it,  have  been  neither  few,  nor  lacking  ingenuity. 
Some  have  attributed  it  to  the  pressure  of  the  atmos- 


94  STOPPING  OF  HEMORRHAGE. 

phere  ;  some,  to  the  vacuum  produced  by  the  dilatation 
of  the  venous  auricle ;  some,  to  muscular  action  ;  and 
some  to  the  sole  and  unassisted  action  of  the  veins 
themselves.  Perhaps  if  the  truth  were  known,  each  of 
these  agents  would  be  found  to  have  a  share  in  produ- 
cing the  effect  in  question. 

The  knowledge  of  the  course  of  the  blood  has  been 
of  signal  service  to  surgeons,  as  well  as  physicians. 
The  older  surgeons,  when  they  cut  off  a  limb,  had  no 
means  of  arresting  the  flow  of  blood  from  the  divided 
vessels,  but  that  of  searing  the  stump  with  a  hot  iron. 
This  answered  the  purpose  for  a  day  or  two,  but  then 
it  generally  broke  out  again,  so  that  the  surgeon  was  kept 
in  constant  dread  of  a  secondary  hemorrhage  which 
would  destroy  his  patient's  life,  before  his  assistance 
could  be  given.  Now,  the  surgeon  ties  up  the  vessels 
with  a  piece  of  silk,  and  goes  away  without  any  appre- 
hension of  being  called  again  to  see  his  patient  floating 
in  his  own  blood.  Besides,  if  the  blood  should  gush 
out  again,  it  can  be  instantly  checked  without  waiting 
for  the  surgeon  to  come  and  tie  up  the  vessels  ;  for 
knowing  the  course  of  the  blood,  all  we  have  to  do  is  to 
press  upon  the  artery  and  the  flow  of  blood  stops  at 
once. 

Emily. — And  this  is  something  which  would  be  ex- 
ceedingly useful  to  other  people  as  well  as  surgeons  to 
know,  for  wounds  of  the  vessels  sometimes  would  de- 
stroy a  person,  before  the  surgeon  could  arrive  and  stop 
the  bleeding.  But,  Dr.  B.,  how  is  every  body  to  know 
the  situation  of  the  artery  which  is  to  be  compressed  ? 

Dr.  B. — If  it  is  not  so  superficial  that  it  can  be  felt, 
as  it  is  in  the  wrist,  a  bandage,  or  a  common  handker- 
chief tied  tight  round  the  limb,  will  effectually  stop  the 
flow  of  the  blood.  Recollect  however,  that  it  is  not  in- 
different on  which  side  of  the  wound  you  use  the  com- 
pression. 

Emily. — That  would  depend  on  the  kind  of  vessel. 
If  an  artery  were  wounded,  the  compression  must  be 


CAPILLARY   VESSELS.  95 

made  between  the  heart  and  the  wound  ;  if  a  vein,  the 
wound  must  be  between  the  heart  and  the  pressure. 
But  I  confess,  I  know  not  how  I  should  ascertain  wheth- 
er it  was  a  vein  or  an  artery  that  was  wounded. 

j)rf  B. — When  blood  flows  from  an  artery,  it  is  by 
jets,  like  air  from  the  nose  of  the  bellows ;  but  from  a 
vein,  it  is  in  a  steady  stream.  The  superficial  veins 
however,  which  are  the  ones  most  frequently  injured, 
are  so  small  that  they  seldom  give  much  trouble,  or 
when  cut  oft,  they  contract  and  thus  prevent  the  escape 
of  blood. 

Emily. — I  do  not  yet  understand  enough  of  the  sub- 
ject to  see  why  a  physician,  when  he  bleeds  a  person, 
always  puts  a  cord  around  the  arms  just  above  where 
the  opening  is  to  be  made. 

Dr.  B. — By  so  doing,  the  blood  is  prevented  from 
passing  along  to  the  heart,  and  accumulates  below  the 
ligature,  so  that  when  an  opening  is  made,  it  gushes  out 
very  freely.  If  no  ligature  were  put  round  the  limb,  a 
little  blood  it  is  true,  would  escape  from  the  opening, 
but  the  greater  portion  would  pass  by  towards  the  heart. 
Hence,  if  after  the  physician  is  gone,  the  bandage  should 
get  loose,  and  the  blood  start,  afresh,  you  would  stop  it 
by  putting  the  cord  around  the  limb  on  the  other  side  of 
the  opening.  But  it  is  time  for  us  to  see  how  the  biood 
is  affected  in  its  passage  through  the  lungs. 

Emily. — But  first  let  me  ask  what  purpose  is  an- 
swered by  the  blood's  going  to  every  part  of  the  body, 
if  it  passes  from  the  arteries  directly  into  the  veins  with 
all  possible  speed. 

Dr.  B. — The  minute  arteries  do  not  terminate  direct- 
ly in  the  veins — at  least,  all  of  them  do  not — but  be- 
tween these  two  sets  of  vessels,  we  find  a  third  set  form- 
ing a  most  delicate  and  intricate  net  work,  and  from 
their  extreme  minuteness,  are  called  capillary  vessels. 
Though  they  communicate  with  both  arteries  and  veins, 
yet  from  their  infinite  division  and  ramification,  and  their 
peculiar  powers,  they  require  us  to  consider  them  as  an 


96        USE  OF  THE  CAPILLARY  VESSELS. 

entirely  distinct  system.  So  extensive  is  their  distribu- 
tion, that  the  most  important  organs  of  the  body  seem  to 
be  almost  wholly  made  up  of  an  immense  network  of 
capillary  vessels.  Owing  to  their  exceeding  minuteness, 
some  of  them  carry  only  the  colorless  portions  of  the 
blood,  the  red  globules  being  too  large  for  their  calibre. 
In  inflammation,  where  the  vessels  are  enlarged,  those 
which  before  transmitted  only  the  colorless  portions, 
may  now  be  seen  carrying  the  red  globules — as  you 
may  have  observed  in  inflammations  of  the  eye.  The 
motion  of  the  blood  in  these  vessels  is  beyond  the  influ- 
ence of  the  heart,  and  under  the  entire  control  of  the 
vessels  themselves.  This  independence  of  action  may 
be  witnessed  in  those  distributed  to  the  face,  which  a 
sudden  emotion  of  mind  will  distend  to  redness  with  the 
rapidity  of  thought. 

Emily. — And  pray,  Dr.  B.,  what  may  be  the  office 
of  this  extensive  system  of  vessels  ?  One  would  think 
they  were  designed  for  some  very  important  and  won- 
derful end. 

Dr.  B. — And  he  would  think  perfectly  right,  for  they 
are  the  seat  of  some  of  the  most  important  functions  in 
the  animal  economy.  From  them  the  peculiar  fluids 
are  secreted,  the  body  is  nourished,  and  many  other 
processes  are  probably  accomplished  which  the  research- 
es of  physiology  have  not  yet  unfolded  to  view.  Their 
number  is  considerably  greater,  where  secretion  is  to  be 
performed,  than  where  their  object  is  only  the  nutrition 
of  the  part.  It  is  for  this  reason  that  the  liver,  stomach, 
&LC.  which  secrete  certain  fluids  that  are  essentially  nec- 
essary to  the  system,  are  supplied  with  a  greater  quan- 
tity than  the  bones,  ligaments  and  skin. 

Their  action  in  repairing  injuries  of  parts,  is  one  of 
great  use  in  the  animal  economy,  and  presents  some 
very  interesting;  and  curious  facts.  When  any  part  is 
injured,  the  capillaries  are  enlarged  and  distended  with 
blood ;  serous  and  fibrous  portions  of  the  blood  are  pour- 
ed out ;  and  heat,  pain,  redness,  and  swelling  are  soon 


THE    ADHESIVE    UNION.  97 

developed.  This  phenomenon  is  called  inflammation, 
and  seems  to  be  a  process  or  action  set  up  in  the  part 
for  the  purpose  of  restoring  the  natural  condition,  for  if 
it  does  not  take  place,  the  injury  is  never  repaired. 
This  restorative  power  is  beautifully  exhibited  in  cases  of 
wounds  made  by  clean-cutting  instruments.  If  the 
edges  of  the  wound  be  immediately  brought  together  and 
retained  in  this  position,  a  quantity  of  fibrine  is  thrown 
out  from  the  capillary  vessels,  which  glues  the  sides  of 
the  wound  firmly  together  ;  vessels  shoot  out  from  either 
side  into  this  mass,  meet  those  of  the  opposite  side,  and 
thus  establish  a  free  circulation  through  it ;  the  firmness 
and  sensibility  of  other  parts  are  shortly  manifested, 
and  it  is  at  last  decidedly  and  completely  organized.  It 
is  astonishing  to  see  with  what  rapidity  this  process  is  some- 
times performed  ;  the  adhesive  matter  was  found  in  one 
case,  to  have  become  completely  organized  in  twenty- 
nine  hours. 

Emily, — With  such  a  palpable  hint,  I  should  suppose 
that  surgeons  would  banish  forever  their  salves  and  oint- 
ments in  curing  wounds,  and  suffer  them  to  be  healed 
by  nature's  own  process.  It  would  be  a  marvellous  cure 
indeed  if  a  surgeon  could  heal  up  a  long,  gaping  wound 
in  twenty  nine  hours,  as  nicely  as  if  nothing  had  ever 
happened. 

Dr.  B. — John  Hunter  first  clearly  understood  this 
process,  towards  the  latter  part  of  the  last  century,  and 
made  it  the  basis  of  one  of  the  greatest  improvements 
that  have  been  made  in  Surgery.  Before  his  time,  sur- 
geons were  generally  accustomed  to  stuff  a  wound  full 
of  lint,  and  balsams,  and  salves,  and  thus  the  simplest 
w»umds  were  weeks  and  even  months  in  healing.  Now 
they  endeavor  always  to  bring  the  sides  of  the  wound 
in  contact,  and  retain  it  there  without  any  other  applica- 
tions. To  see  to  what  extent  this  union  between  divi- 
ded parts  might  be  carried,  Mr.  Hunter  cut  off  the  spur 
from  a  cock's  foot,  and  making  a  slight  incision  into  the 
comb,  he  placed  the  spur  into  the  wound  and  bound  it 


98  THE    ADHESIVE    UNION. 

up.  The  result  was,  that  they  united,  and  the  spur  con- 
tinued to  grow  on  the  comb. full  as  well  as  it  had  done  in 
its  natural  position.  The  same  effect  took  place,  when 
he  removed  a  tooth  from  a  man,  and  engrafted  it  on  a 
cock's  comb.  Fingers,  after  having  been  completely 
chopped  off,  have  been  bound  to  the  stumps  and  be- 
come perfectly  united  to  them.  In  cases  of  wounds 
where  there  is  a  deficiency  of  substance,  surgeons  have 
lately  adopted  the  practice  of  supplying  the  deficiency 
by  strips  of  flesh  removed  from  other  parts  of  the  body. 
In  the  East  Indies  where  it  is  the  practice  of  the  chiefs 
to  cut  off  the  noses  of  their  prisoners,  the  operation  is 
frequently  practised  of  making  a  new  nose,  out  of  a 
strip  of  flesh  that  is  cut  from  the  forehead,  but  still  ad- 
hering by  one  extremity,  and  made  to  unite  with  the 
stump  of  the  absent  member. 

Emily. — I  think  I  have  heard  of  this  operation  be- 
fore, but  always  supposed  it  was  merely  an  idle  tale. 
But  pray  Dr.  B.  what  kind  of  a  figure  does  the  new 
nasal  member  make  in  the  man's  countenance  ? 

Dr.  B. — It  is  said  that  some  very  handsome  noses 
have  been  made  in  this  way.  You  must  admit  that  there 
is  certainly  one  advantage  gained  by  having  a  nose  thus 
made  to  order  ; — you  can  consult  your  own  taste  about 
its  shape  as  you  would  the  cut  of  your  coat,  and  have  it 
Grecian,  or  Roman,  or  in  any  other  style,  according  to 
the  fashion  which  happens  to  be  in  vogue,  or  as  it  har- 
monizes with  the  other  features. — This  closes  the  histo- 
ry of  the  Circulation.  In  our  next  conversation  we  shall 
examine  the  organs  and  functions  of  respiration. 


RESPIRATORY    ORGANS.  99 


CONVERSATION  V. 


Respiration — the  lungs — the  thorax — mechanism  of 
inspiration — changes  wrought  on  the  air  by  respiration 
— relation  of  these  changes  to  those  wrought  on  the 
blood — animal  heat — respiration  of  Fishes — of  Birds — 
of  Reptiles — of  Mollusca  and  Insects — of  Spiders. — Se- 
cretion— various  kinds  of  Secretions — Secretion  in  the 
inferior  animals. — Jfbsorbtion — performed  chiefly  by  the 
veins — the  lymphatics — the  lymph. — Nutrition. 

Dr.  B.  To  day  we  are  to  consider  the  changes  which 
the  blood  undergoes  in  its  passage  through  the  lungs, 
and  the  mechanism  of  the  parts  concerned  in  producing 
them.  The  respiratory  organs  are  two  light,  spongy, 
and  rather  irregularly  shaped  bodies,  placed  in  the  tho- 
rax, or  chest,  one  on  each  side,  called  the  Lungs.-^- 
They  are  composed  almost  entirely  of  air-cells  and 
blood  vessels,  though  some  other  tissue  is  probably  pre- 
sent, which  serves  as  a  common  bond  of  union.  These 
little  air-cells,  which  are  of  extreme  minuteness,  are 
distributed  to  every  portion  of  the  organ,  and  seem  to 
be  the  ultimate  ramifications  of  two  large  tubes,  which 
lead,  one  to  each  lung,  called  the  bronchiae.  The  blood 
vessels  belong  to  the  capillary  system,  and  communicate 
with  the  pulmonary  arteries  and  veins.  They  are 
situated  in  the  tissue  of  the  cells,  and  it  is  while  the 
blood  is  passing  through  them,  that  it  is  subjected  to 
the  respiratory  process.  The  bronchiae  are  the  subdi- 
visions of  a  single  tube,  called  the  trachea,  or  windpipe. 


RESPIRATORY    ORGANS. 


which  is  situated  in  the  neck,  directly  over  the  oesopha- 
gus, and  communicates  with  the  mouth  by  an  opening, 
which,  you  will  recollect,  we  have  already  noticed. 

Emily. — The  chink  of  the  glottis — one  of  the  seven 
openings  into  the  pharynx  ;  I  recollect  it. 

Dr.  B. — The  air-tubes,  and  perhaps  the  air-cells,  are 
lined  with  mucous  membrane  similar  to  ihat  which  lines 
the  alimentary  canal.  In  this  engraving  you  have  a  di- 


agram  of  the  lungs,  and  thebronchiae  leading  into  them, 
toether  with  the  distribution  and  re-union  of  the  vessels. 


JHECHANISM    OP    RESPIRATION.  101 

They  are  covered  externally  by  a  smooth,  shining  mem- 
brane called  the  pleura— the  same  kind  of  membrane, 
that  lines  the  walls  of  the  chest  and  abdomen,  and  forms 
the  external  coat  of  the  alimentary  canal.  While  in 
action,  they  completely  fill  the  cavity  of  the  chest,  that 
is  not  occupied  by  other  organs,  so  that  no  empty  space 
is  ever  left. 

Emily. — -What  an  admirable  system  of  machinery  is 
here !  I  never  imagined  however,  that  the  lungs  were 
sufficiently  large  to  fill  almost  the  whole  cavity  of  the 
chest. 

Dr.  B.^To  understand  how  the  air  gets  admittance 
into  the  lungs,  we  must  first  examine  the  structure  and 
mechanism  of  the  chest.  Its  form  is  conoidal,  the  apex 
being  at  the  top,  and  the  base  at  the  bottom.  Behind, 
it  is  bounded  by  the  spine ;  at  the  sides,  by  the  ribs ;  in 
front,  by  the  sternum  or  breast  bone  ;  below,  by  a  thin 
membranous  muscle,  called  the  diaphragm  or  midrif, 
which  forms  the  floor  of  its  base,  and  separates  it  from 
the  cavity  of  the  abdomen.  .These  parts  are  joined  to- 
gether in  such  a  manner,  that  considerable  motion  is  al- 
lowed between  them,  and  by  this  means  the  capacity  of 
the  chest  may  be  considerably  enlarged  and  diminished. 
The  depression  of  the  diaphragm  enlarges  the  chest  at  the 
expense  of  the  abdomen,  while  the  ribs  being  thrust  for- 
ward and  upward  by  means  of  the  numerous  muscles, 
that  are  attached  to  them,  produce  an  enlargement  in 
the  other  directions.  The  lungs  follow  the  variations  of 
capacity  in  the  chest,  expanding  their  air-cells,  when 
the  latter  is  enlarged,  so  as  still  to  fill  up  the  whole  cav- 
ity, and  collapsing,  when  the  chest  is  contracting.  Now 
observe  how  they  become  filled  with  air.  Suppose  that 
expiration  has  just  taken  place,  the  lungs  in  a  collapsed 
state,  and  the  chest  reduced  to  its  smallest  capacity. 
This  state  of  things  can  last  but  a  few  moments.  The 
necessity  of  fresh  air  is  felt,  and  we  instinctively  expand 
the  chest.  The  lungs  follow  the  expanding  walls  of  the 
chest,  and  consequently  a  vaciuim  is  produced  in  their 

0* 


102  CHANGES    EFFECTED    IN    THE    BLOOD 'i 

cells.  The  external  air,  with  which  they  freely  con* 
municate,  accordingly  rushes  in  through  the  mouth  and 
nostrils,  and  fills  the  vacuum  as  fast  as  it  is  made. 

Emily. — But  I  had  always  supposed  that  the  chest 
arid  lungs  expanded,  in  consequence  of  the  admission 
of  the  air. 

Dr.  J3. — To  be  convinced  that  you  are  wrong,  you 
have  only  to  open  your  mouth  and  nostrils  as  wide  as 
you  please,  and  see  if  the  air  ever  rushes  in,  till  by  a 
voluntary  effort,  you  begin  to  expand  the  chest.  A  per- 
son would  breathe  equally  as  well,  if  the  mouth'  and 
nostrils  were  closed,  and  an  opening  made  in  the  wind- 
pipe. When  the  chest  contracts,  the  air  is  consequent- 
ly expelled,  and  thus  are  produced,  in  constant  succes- 
sion, the  two  acts  of  inspiration  and  expiration. 

Emily. — According  to  this  then,  these  acts  are  alto- 
gether involuntary,  and  yet  you  know  we  can  delay  ei- 
ther of  them  a  few  moments,  and  I  have  heard  of  peo- 
ple, whose  business  is  to  dive  for  pearls,  who  could  re- 
main underwater  a  half  hour  at  a  time.  These  facts 
prove  at  least,  that  the  function  is  in  some  measure  un- 
der the  will. 

Dr.  13. — These  cases  are,  in  all  probability,  great 
exaggerations,  though  people  can,  no  doubt,  by  educa- 
tion extend  the  influence  of  the  will  over  this  function 
to  a  certain  extent,  in  the  same  manner  as  we  can  ac- 
custom our  constitution  to  a  less  quantity  of  food  or  ex- 
ercise. Still  the  action  is  strictly  involuntary — try  as 
hard  as  you  may,  to  suspend  the  act  of  inspiration,  the 
muscles  will  invariably  contract  and  expand  the  chest, 
in  spite  of  your  exertions. 

Emily. — Supposing  now  the  air  to  have  penetrated 
into  the  cells  of  the  lungs — I  cannot  imagine  how  it  is 
to  affect  the  blood.  In  the  first  place,  however,  I  should 
more  properly  ask,  what  changes  in  the  blood  it  does 
produce. 

J>r.  B. — The  blood  conveyed  to  the  lungs,  is  from 
fi  modena  red  converted  into  a  bright  scarlet  color  :  itt- 


CHANGES    EFFECTED    IN    THE    AIR.  103 

odour  is  more  pungent  ;  its  temperature  is  from  98°  of 
Far.  raised  to  100°  ;  its  capacity  for  caloric  is  a  lit- 
tle lessened ;  it  coagulates  more  quickly,  and  is  less 
abundant  in  serum. 

Emily. — Now  I  may  ask  how  these  changes  are  pro- 
duced ? 

j}Tf  B. — And  truly  a  question  more  easily  asked 
than  answered.  But  at  any  rate  we  can  tell  pretty  ex- 
actly, what  changes  the  air  itself  has  undergone,  and  if 
it  were  true,  as  was  once  said  by  royal  lips,  that  "  in 
a  multitude  of  counsellors  there  is  wisdom,"  we  might 
be  exceedingly  wise  concerning  the  changes  that  are 
produced  in  the  blood.  The  air,  which  we  breathe, 
is  composed,  you  know,  of  two  gases,  oxygen  and  nit- 
rogen— 21  parts  of  the  former,  and  about  78  of  the  lat- 
ter. Besides  these,  there  is  generally  found  a  very 
small  portion  of  carbonic  acid — about  1  part.  Such  is 
the  composition  of  the  air  when  it  goes  into  the  lungs, 
but  not  such  when  it  comes  out.  If  we  examine  a  quan- 
tity of  expired  air,  we  shall  find  that  the  oxygen,  instead 
of  forming  21  parts  of  it,  now  forms  only  18  or  19  parts, 
that  the  carbonic  acid  amounts  to  3  or  4  parts,  and  that 
the  nitrogen  is  not  apparently  increased  or  diminished. 
So  you  see  that  oxygen  alone  is  made  use  of  in  the  per- 
formance of  this  function  ;  and  the  rapidity  with  which 
its  deprivation  causes  the  death  of  any  living  being,  well 
entitles  it  to  be  considered  as  the  grand  supporter  of  liv- 
Sng  action. 

Emily. — Since  the  nitrogen  is  returned  unchanged  in 
quantity,  what  can  possibly  be  its  use  in  respiration  ? 
Would  not  an  air  of  pure  oxygen  answer  the  purpose 
just  as  well  ? 

Dr.  B. — Though  we  are  unable  to  see  what  part  the 
nitrogen  takes  in  the  process,  numerous  experiments 
prove  that  it  is  not  useless,  nor  to  be  dispensed  with ; 
for  though  an  animal  will  live  four  times  longer  in  pure 
oxygen,  than  in  the  same  quantity  of  atmospheric  air, 
yet  when  breathed  for  any  length  of  time,  the  organ0 


104  THEORIES    OF    RESPIRATION. 

become  stimulated  beyond  measure,  and  death  is  the 
consequence. 

What  the  chemical  changes  are,  which  respiration  pro- 
duces in  the  blood — what  it  receives  and  loses,  aiv  points 
which  have  occupied  considerable  attention  from  chem- 
ists and  physiologists,  and  given  rise  to  experiiiK-  -ts, 
whose  results  are  any'  thing  but  harmonious.  To  ac- 
count for  the  carbonic  acid  in  the  expired  air,  some  say 
that  carbon  is  secreted  from  the  venous  blood,  into  the 
air-cells  of  the  lungs,  and  there  unites  with  the  oxygen, 
forming  carbonic  acid.  They  say  that  the  only  use  of 
the  oxygen,  is  to  decarbonise  the  venous  blood,  and  that 
no  more  oxygen  is  consumed,  than  is  necessary  for  this 
purpose  ;  that  no  oxygen  enters  into  the  arterial  blood, 
but  its  florid  hue  is  the  result  of  its  loss  of  carbon. 
The  promulgator  of  this  doctrine  was  Mr.  Ellis,  of 
Edinburgh,  and  he  applied  it  to  the  respiration  of  plants. 
His  experiments  are  numerous,  and  seem  quite  satisfac- 
tory. Others  say,  that  oxygen  does  enter  the  blood,  and 
that  it  is  the  chief  object  of  respiration,  to  supply  the 
blood  with  this  vivifying  substance.  The  carbonic  acid 
in  the  expired  air,  they  say,  is  secreted  from  the  venous 
blood.  This  was  thex  theory  of  Lavoiser,  the  celebra- 
ted French  chemist.  The  experiments  of  Dr.  Ed- 
wards, of  Paris,  prove  that  carbonic  acid  is  formed  in 
the  blood  vessels,  because  the  same  quantity  of  car- 
bonic acid  is  given  out  when  the  animal  breathes  hy- 
drogen gas,  as  when  he  breathes  atmospheric  air.  It 
seems  probable  too,  that  some  of  the  carbonic  acid  is 
formed  in  the  way  which  Mr.  Ellis  supposes.  Oxygen 
is  of  course  absorbed,  and  while  circulating  in  the  ves- 
sels, it  probably  unites  with  the  carbon,  and  forms  the 
carbonic  acid,  that  is  secreted,  though  this  is  not  the  on- 
ly source  oi  this  gas. 

Emily. — But  now  I  do  not  understand  any  better,  how 
the  changes  in  the  air  produce  the  changes  in  the  blood, 
which  you  mentioned.  I  see  no  manner  oi  connection 
between  these  two  set*;  of  facts. 


THEORIES    OF    RESPIRATION.  105 

Dr.  B. — About  all  the  physical  changes  produced  in 
the  blood  by  respiration  can  be  more  satisfactorily  ex- 
plained by  admitting  the  presence  of  oxygen,  than  mere- 
ly a  loss  of  carbon.  The  fact  then  that  they  are  owing 
to  a  fresh  supply  of  oxygen  is  nearly  all  we  know  of  it ; 
how  it  should  have  this  effect,  we  cannot  explain. 

Emily. — That  carbon  in  some  form  or  other  is  emit- 
ted from  the  blood  in  respiration,  is  one  fact  at  least  in 
which  they  all  agree.  The  decarbonizatipn  of  the  blood 
then,  is  one  object  of  the  function,  whether  its  oxygena- 
tion  be  another  or  not ;  but  I  do  not  understand  where 
all  this  carbon  comes  from. 

Dr.  B. — You  must  recollect  that  it  is  into  veins  that 
the  nutritious  aliment  prepared  by  digestion,  is  poured, 
as  well  as  a  considerable  portion  of  those  particles  of  the 
body  that  have  become  unfit  for  nutrition  and  require  to 
be  removed  from  the  system.  These  materials  all  abound 
with  carbon,  and  it  is  from  this  source  that  the  carbon  in 
the  venous  blood  is  derived. 

Emily. — It  has  just  occurred  to  me,  Dr.  B.,  that  if 
these  chemical  changes  are  actually  going  on  in  the 
lungs,  they  ought  to  be  accompanied  with  their  usual  re- 
sults. The  union  of  carbon  with  oxygen,  so  as  to  form 
carbonic  acid  gas,  is  attended  with  a  disengagement  of 
heat,  as  any  one  may  know  who  ever  sat  by  a  charcoal 
fire. 

Dr.  B. — And  so  you  would  expect  that  the  lungs,  not 
being  made  of  exactly  fire-proof  materials,  must  inevita- 
bly get  scorched  ? 

Emily. — Rather  an  unpleasant  conclusion  indeed,  but 
really,  I  see  not  how  it  can  be  avoided. 

Dr.  B. — No  sooner  were  the  chemical  changes  that 
are  effected  in  the  lungs,  brought  to  light,  than  physiolo- 
gists began  to  connect  the  production  of  animal  heat  with 
the  function  of  respiration.  At  first  it  was  imagined  that 
the  lungs  themselves  were  the  grand  furnace  in  which 
the  caloric  was  manufactured,  that  was  to  be  taken  up  by 
the  blood  vessels  and  carried  to  every  portion  of  the  syS- 


106  ANIMAL    HEAT. 

tern.  Finding  afterwards  that  the  consequences  which 
you  suggested  rendered  this  theory  untenable,  they  con- 
cluded at  last  that  the  oxygen  was  absorbed  into  the  ves 
sels,  and  that  its  combination  with  carbon,  and  the  con- 
sequent disengagement  of  heat,  took  place  gradually 
throughout  the  whole  venous  system.  Thus  a  constant 
and  equal  warmth  is  diffused  over  the  whole  body. 

Emily. — What  a  beautiful  theory  !  How  admirably 
the  greatest  results  are  sometimes  effected  by  apparent- 
ly the  most  ordinary  agents. 

Dr.  13. — Beautiful  indeed  it  is ;  but  unhappily  we 
cannot  speak  so  favorably  of  its  truth.  The  venous 
blood  in  which  the  carbonic  acid  is  supposed  to  be  form- 
ed, instead  of  indicating;  a  higher  temperature  than  the 
arterial  blood,  as  it  evidently  ought,  is  even  two  or  three 
degrees  lower.  This,  together  with  many  other  facts 
which  have  been  established  by  later  experiments,  have 
now  pretty  generally  discredited  the  theory,  and  Physi- 
ologists have  been  obliged  to  turn  their  attention  to 
some  other  source  for  an  explanation  of  the  effect  ia 
question. 

Emily. — If  the  same  theory  was  expected  to  apply 
to  the  respiration  of  plants,  it  must  inevitably  have  been 
falsified  there.  Plants  have  a  temperature  above  that 
of  the  atmosphere  in  the  middle  of  winter.  I  have  of- 
ten observed  that  the  snow  which  falls  on  their  limbs 
and  around  their  roots,  soon  melts  away,  and  Dr.  S. 
mentioned  last  summer  in  his  botanical  lectures,  that  if 
the  bulb  of  a  thermometer  be  introduced  into  the  trunk 
of  a  tree  in  the  coldest  day,  the  mercury  will  rise  above 
the  freezing  point.  At  this  time  their  branches  are  des- 
titute of  foliage  and  no  respiration  can  consequently  be 
going  on. 

Dr.  B. — We  are  not  positive  that  vegetable  heat  and 
animal  heat  are  both  produced  in  the  same  way  ;  but 
still  if  you  had  been  sufficiently  acquainted  with  the 
subject,  you  might  have  adduced  analogies  from  the  an- 
imal kingdom,  equally  conclusive.  Many  reptiles  lie  in 


ANIMAL    HEAT. 


lor 


a  torpid  state  for  months  together,  when  the  function  of 
respiration  is  wholly  suspended,  and  still  their  tempera- 
ture is  above  that  of  the  surrounding  medium.  Some 
late  experiments  of  Mr.  Brodie  seem  to  show  that  the 
production  of  animal  heat  is  entirely  independent  of  res- 
piration. He  inflated  the  lungs  of  an  animal  after  death 
and  maintained  an  artificial  respiration.  The  usual 
changes  continued  to  be  wrought  on  the  blood  ;  it  was 
converted  from  its  modena  hue  to  bright  scarlet,  and 
carbonic  acid  was  formed,  but  the  body  lost  its  heat  as 
fast  as  if  it  had  been  suffered  to  remain  at  rest. 

Emily. — But,  Dr.  B.,  are  we  to  give  up  the  point  in 
despair  and  consider  it  wholly  beyond  our  power  of  ex- 
planation ? 

Dr.  B. — It  has  been  lately  suggested  that  it  might  be 
the  result  of  a  peculiar  action  of  the  nervous  system  on 
the  capillary  vessels  ;  but  no  attempt  having  been  made 
to  establish  it  by  a  systematic  array  of  proofs  and  argu- 
ments, it  is  as  yet  merely  a  suggestion. 

Emily. — If  you  had  not  objected  to  my  analogy 
drawn  from  the  vegetable  kingdom,  I  should  say  that 
this  theory  was  equally  unsupported  by  it,  for  I  never  as 
yet  heard  that  plants  possess  a  nervous  system. 

Dr.  B. — They  have  not  a  nervous  system  it  is  true, 
but  for  any  thing  we  know,  particles  of  nervous  matter 
may  be  diffused  through  their  structure,  and  capable  of 
producing  the  same  effects  in  regard  to  vegetable  heat, 
that  a  proper  nervous  system  does  in  regard  to  animal 
heat.  But  although  we  are  unable  to  explain  the  cause 
of  this  phenomena,  the  facts  connected  with  it  are  no 
less  certain,  or  interesting.  Some  of  them  are  as  curi- 
ous as  they  are  inexplicable,  particularly  the  power  of 
organized  bodies  to  preserve  a  uniform  temperature  not- 
withstanding the  changes  in  the  surrounding  medium. 
Thus  the  temperature  of  the  human  body  is  between 
98°  and  99°  of  Far.  whether  we  examine  it  in  the  Esqui- 
maux who  dwells  in  his  icy  hut  under  the  polar  circle, 
or  the  Negro  who  feels  the  scorching  rays  of  an  equato- 
rial sun. 


108  EXPERIMENTS    ON    ANIMAL    HEAT. 

Emily. — But  would  not  their  temperature  change,  if 
each  were  removed  to  the  country  of  the  other  ?  Place 
the  Esquimaux  in  the  torrid  zone,  and  I  think  he  would 
feel  a  little  warmer,  and  even  you  or  I  would,  though 
the  transition  would  be  much  less. 

Dr.  JB. — Of  course,  then,  ii  you  would  be  consistent, 
you  suppose  that  our  temperature  is  greater  in  summer, 
than  io  winter.  No  ;  the  temperature  of  the  body  re- 
mains the  same  through  all  the  seasons.  Our  feelings 
are  no  test  of  the  temperature  as  indicated  by  a  ther- 
mometer. Even  in  the  midst  of  a  raging  fever,  when 
the  person  feels  as  if  he  were  actually  burning  up,  the 
thermometer  will  often  indicate  a  degree  of  heat,  a  little 
less  than  that  of  ordinary  health ;  while  in  the  cold  pa- 
roxysms, when  he  is  shivering  from  head  to  foot,  it  may 
indicate  a  degree  or  two  more.  It  is  astonishing  to  see 
how  great  a  degree  of  heat  the  body  will  stand,  and  still 
retain  its  natural  temperature.  Under  the  observation  of 
the  Academy  of  Science,  in  France,  two  girls  entered 
an  oven  where  fruits  were  baking,  and  stayed  there  sev- 
eral minutes,  without  suffering  any  ill  effect.  Reaumur's 
thermometer,  which  they  carried  with  them  in  their 
hands,  stood  at  150°,  equal  to  337  1-2  of  Far. 

Emily. — -The  story  of  Sir  Joseph  Bankes,  Dr.  For- 
dyce,  and  Dr.  Blagden's  attempting  to  ascertain  how 
high  a  degree  of  heat  the  system  could  withstand,  is 
also  very  interesting.  A  suit  of  three  rooms  heated  by 
flues  in  the  floor,  was  prepared,  into  which  they  entered, 
without  taking  oft  their  clothes.  When  -they  first  en- 
tered, the  mercury  in  Far.  stood  at  1 50°,  and  they  con- 
tinued 20  minutes  ;  during  which  time,  the  mercury 
rose  12°  higher.  At  another  time,  the  mercury  stood 
at  198°,  and  they  continued  in  this  heat  )0  minutes. — 
In  a  heat  of  21 1°  at  first,  Sir  J.  Bankes  remained  7  min- 
utes; in  which  time  the  mercury  sunk  to  198°.  All 
this  time,  the  temperature  of  their  bodies  rose  very  lit- 
tle above  its  ordinary  state.  Whenever  they  breathed 
on  the  thermometer,  the  mercury  sunk  several  degrees ; 


EFFECT    OE    COLD    ON    ANIMAL    HEAT.  109 

every  expiration  afforded  a  pleasant,  cooling  impression 
to  the  nostrils,  and  their  breath  cooled  their  fingers.  Dr. 
Blagden,  on  touching  his  side,  found  it  felt  like  a  corpse. 
Their  watch  chains,  and  pieces  of  metal,  which  they  had 
in  their  pockets,  were  so  hot  that  they  could  scarcely 
touch  them.  In  subsequent  experiments,  the  heat  of 
the  room  was  240°,  and  even  260°.  These  excessive 
degrees  of  heat  they  bore  without  experiencing  any  in- 
jurious effects.  The  circulation  was  raised  to  140°  in 
a  minute,  and  their  perspiration  was  extremely  copi- 
ous, running  down  in  streams  over  their  bodies.  I  do 
not  recollect  all  the  details  of  the  account,  but  these  are 
the  principal  facts, 

Dr.  B. — Before  we  quit  this  subject,  we  shall  find  it 
interesting  to  look  a  moment  or  two,  at  the  various 
modes,  in  which  the  respiratory  function  is  managed  in 
the  lower  orders  of  animals. 

Emily. — I  am  glad  you  have  proposed  this,  for  I  nev- 
er could  conceive  how  this  function  is  managed  in  fishes, 
for  they  surely  have  no  access  to  the  air.  But  first  let 
me  ask  if  the  human  constitution  manifests  a  similar 
power  of  preserving  its  own  temperature,  in  exposures  to 
extreme  cold,  as  well  as  heat? 

Dr.  B. — Its  power  in  this  respect  is  no  less  wonder- 
ful than  in  the  other ;  some  astonishing  instances  of  it 
have  been  from  time  to  time  recorded  by  voyagers  and 
travellers.  Lewis  and  Clarke  relate  that  two  Indians,  a 
man  and  a  boy,  slept  on  the  snow  in  an  ordinary  light 
dress  when  the  mercury  in  the  thermometer,  at  sunrise, 
was  40°  below  zero.  The  man  suffered  no  inconven- 
ience ;  the  boy  had  his  feet  frozen,  but  they  were  re- 
covered by  cold  water. 

Emily. — I  recollect  a  striking  fact  of  this  nature  re- 
corded by  Capt.  Lyon,  in  the  Journal  of  his  voyage  to 
the  polar  regions.  He  says  that  he  often  saw  the  young 
Esquimaux  children  exposed  half  naked  to  the  open  air, 
when  the  mercury  was  32°  below  zero  ;  and  that  too, 
without  suffering  any  apparent  inconvenience. 
10 


110  RESPIRATION    OF    FISHES. 

Dr.  B. — And  how  much  more  astonishing  it  is  that 
Europeans  who  have  been  accustomed  to  warmer  cli- 
mates, should  be  able  by  using  the  proper  precautions, 
to  bear  such  severe  cold,  with  equal  impunity.  The 
English,  at  one  of  their  trading  houses  on  the  Churchill 
river,  experienced,  one  year,  such  a  degree  of  cold  that 
brandy  froze  in  the  rooms  where  they  had  fires. 

Emily. — Ledyard,  I  recollect,  experienced  in  Yak- 
utsk, Siberia,  a  degree  of  cold  which  coagulated  strong 
cogm'ac  brandy. 

Dr.  13. — Many  more  observations  of  a  similar  kind 
might  be  mentioned,  but  these  are  sufficient  to  show  how 
independent  of  external  changes,  is  the  temperature  of 
our  bodies. 

I  will  now  describe  to  you  how  the  function  of  respira- 
tion is  managed  in  fishes.  They  cannot  obtain  access  to 
the  atmosphere,  it  is  true,  but  there  is  always  a  quantity 
of  air  mixed  with  the  water  in  which  they  live,  and  they 
are  furnished  with  organs  fitted  for  separating  it  and  ap- 
plying it  to  the  same  purpose  as  the  lungs  of  animals. 
Instead  of  lungs  in  the  interior  of  their  body,  they  are 
provided  on  e?ch  side  of  the  neck  with  several  thin,  red 
laminae  of  a  semi-circular  form,  called  branchiae  or  gills. 
These  are  attached  to  the  bones  and  covered  with  a 
moveable  lid.  In  these  gills  are  ramified  the  extremi- 
ties of  the  pulmonary  arteries  and  veins,  and  also  the 
capillary  vessels  in  which  the  necessary  changes  are 
wrought  on  the  blood. 

Emily. — I  have  heard  that  if  fishes  were  kept  in  close 
vessels,  and  communication  with  the  atmosphere  cutoff 
they  would  soon  die,  but  never  knew  before  that  it  was 
for  lack  of  air ;  for  I  suppose  their  death  is  produced  in 
consequence  of  all  the  air  in  the  water  being  consumed. 
But  is  it  not  strange  that  they  should  die  so  soon  when 
taken  out  of  the  water,  merely  because  they  breathe 
pure  air,  and  not  air  in  combination  with  water  ? 

Dr.  B. — This  is  sufficient  to  produce  their  death,  for 
their  respiratory  organs  are  constructed  for  breathing  air 


HEAT    OF    FISHES.  Ill 

only  in  the  manner  in  which  they  do.  But  this  is  not 
the  only  cause,  since  if  a  fish  have  his  head  and  gills  im- 
mersed in  water,  and  the  rest  of  his  body  exposed  to  the 
atmosphere,  he  will  not  live  but  a  few  days.  Death 
seems  to  be  occasioned  by  an  excessive  loss  of  matter 
by  transpiration  from  the  exposed  surface  of  the  body, 
and  to  a  change  in  the  pressure  of  the  surrounding  medi- 
um, as  well  as  to  the  un  fitness  of  the  gills  to  act  upon 
the  atmosphere. 

Emily. — Do  tell  me,  Dr.  B.,  why  fishes  are  called 
cold-blooded  animals  ?  They  no  doubt  have  a  certain 
temperature  which  is  unaffected  by  external  changes. 

Dr.  B. — They  are  called  cold-blooded  because  their 
temperature  is  very  low  compared  with  ours,  though  it  is 
generally  a  little  above  that  of  their  usual  medium.  The 
standard  heat  of  fresh  water  fishes  is  60°  ;  that  of  those 
of  the  sea,  about  50°.  What  is  exceedingly  singular  in 
regard  to  the  animal  heat  of  fishes,  is  that  it  is  considera- 
bly modified  by  external  temperature.  Mr.  Hunter  put 
an  eel  whose  heat  was  44°,  while  that  of  the  atmosphere 
was  the  same,  into  water  heated  to  65°  for  fifteen  min- 
utes ;  upon  examination  at  the  end  of  that  period,  it  was 
found  to  be  of  the  same  degree  of  heat  with  the  water. 
Having  put  an  eel,  the  heat  in  whose  stomach  was  37°, 
into  a  freezing  mixture,  its  temperature  sunk  to  31Q. 
The  animal  at  that  time  appeared  dead,  but  next  day  it 
was  alive.  At  another  time  he  put  a  living  and  dead  eel 
and  a  living  and  dead  tench — a  fish  not  found  in 
our  waters ;  it  belongs  to  the  same  family  with  the  carp 
— into  warm  water  ;  they  all  received  heat  equally 
quick,  and  when  they  were  exposed  to  cold,  both  the 
living  and  dead  lost  their  heat  with  equal  quickness.  It 
is  strange  too,  to  see  in  what  a  hot  medium  fishes  some- 
times live.  Sonnerat  declares  that  he  saw  in  the  Phil- 
lipine  islands,  fishes  swimming  in  water  whose  heat  was 
187°  of  Far. 

Emily. — Why,  an  access  of  a  few  more  degrees  of 


112  RESPIRATION    OF    REPTILES. 

heat  would  boil  them  alive.  I  presume  they  are  cautious 
how  they  take  exercise  in  such  a  terrifying  medium. 

Dr.  B. — The  respiration  and  circulation  of  birds  are 
upon  the  same  plan  as  those  of  man  and  the  large  quad- 
rupeds. These  functions  possess  a  higher  degree  of  ac- 
tivity than  in  the  last  animals,  and  in  fact  may  be  consid- 
ered as  at  their  maximum  in  the  Bird.  Birds  have  no 
diaphragm;  the  lungs  adhere  to  the  ribs  and  extend  far 
down  into  the  abdomen  ;  and  the  chest  does  not  change 
its  capacity  in  respiration.  The  air  is  admitted  into  and 
expelled  from  the  lungs  solely  by  their  own  force.  Their 
animal  heat  is  also  greater  than  that  of  any  other  ani- 
mals, and  may  be  stated  as  varying  from  104°  to  107° 
of  Far. 

From  a  few  experiments  that  have  been  made,  it  ap- 
pears that  birds  are  less  capable  of  resisting  the  extremes 
of  heat  and  cold,  than  other  animals.  The  migrations 
of  birds  are  evidently  for  no  other  purpose  than  to  avoid 
those  extremes  of  temperature  incident  to  many  regions. 
The  swallows  are  unable  to  bear  the  cold  of  the  New 
England  September,  and  a  little  premature  cold  weather, 
hastens  their  departure  several  days,  if  not  weeks.  Of 
all  the  birds  that  enliven  our  fields  in  summer,  not  one 
remains  to  share  with  us  the  rigors  of  the  cold  and  drea- 
ry season.  Even  the  little  snow-bird  which  forms  such 
a  lively  feature  in  our  winter  scenery,  has  come  from 
higher  and  colder  regions,  to  enjoy  a  more  genial  climate 
in  ours. 

Emily. — I  used  frequently  to  see  them  in  the  country, 
and  though  they  seemed  gay  and  active,  as  they  flew 
along  from  one  field  to  another,  yet  I  pitied  them,  for  I 
thought  such  tender  things  must  suffer  from  the  cold. 

Dr.  B. — The  respiratory  organs  of  reptiles,  though 
formed  for  breathing  atmospheric  air,  are  less  perfe'ct  in 
their  organization  than  the  lungs  of  other  animals.  In- 
stead of  consisting  of  solid  fleshy  organs,  penetrated 
throughout  with  innumerable  air-tubes,  they  are  com- 
posed of  numerous  delicate  membranous  bags,  communi- 


RESPIRATION    OF    REPTILES.  113 

eating  together,  and  occupying  considerable  space  on 
the  sides  of  the  body.  The  air  is  swallowed  through 
the  nostrils  by  a  peculiar  working  of  the  jaws,  and  is  ex- 
pelled by  the  action  of  the  abdominal  muscles.  This 
sort  of  lungs  is  capable  ol  acting  on  but  a  comparatively 
small  portion  of  blood,  and  now  if  we  look  at  the  circu- 
lation of  these  creatures,  we  shall  see  how  admirably 
these  two  functions,  respiration  and  circulation,  corres- 
pond to  each  other. 

The  circulation  of  Reptiles  has  this  peculiarity  which 
distinguishes  it  from  that  of  all  other  classes — the  blood 
which  is  brought  from  both  the  body  and  the  lungs,  is 
poured  into  a  single  reservoir,  or  into  two  or  three, 
which  finally  communicate,  where  it  is  mingled  together, 
and  thence  sent  back  again  to  the  lungs  and  body. 

Emily. — Then  some  portion  of  the  blood  sent  away 
to  nourish  the  body,  is  venous,  and  some  of  that  sent  to 
the  lungs  to  be  renovated  by  their  action,  is  arterial,  and 
of  course  does  not  need  their  action.  Why,  what  can  be 
the  reason  of  this  ?  I  should  think  they  would  suffer  the 
fate  of  the  blue-boys,  whom  you  spoke  of  yesterday. 

Dr.  B. — The  nature  of  their  lungs  is  such,  that  they 
are  unfitted  for  acting  on  blood  which  is  wholly  venous  ; 
it  would  require  a  greater  amount  of  action  than  they 
are  capable  of.  So  too,  if  the  arteries  carried  only  ar- 
terial blood  to  the  body,  it  would  be  renovated  and  ex- 
cited beyond  its  proper  measure. 

Emily. — Still,  I  do  not  understand  clearly,  why  this 
inactivity  of  respiration  and  circulation,  should  be  so 
particularly  necessary  to  Reptiles,  or,  to  use  the  lan- 
guage of  writers  on  natural  theology,  I  do  not  perceive 
the  final  cause. 

Dr.  B. — This  is  not  very  obvious,  though  generally 
it  does  appear  very  clearly  to  depend  on  their  habits  of 
life.  Most  of  them  live  in  the  water,  and  are  obliged  to 
remain  under  the  water  for  very  long  periods  before  com- 
ing up  to  breathe  ;  an  active  respiration,  like  man's  or  the 
birds',  would  obviously  be  incompatible  with  such  a  mode 
10* 


114  HEAT    OF    THE    MoLLUSCA. 

of  life.  Others  live  in  confined  and  dirty  places,  where 
they  are  obliged  to  breathe  foul  and  noxious  gases, 
which  would  suffocate  animals  of  more  active  respiration. 
It  is  curious  to  see  how  long  they  can  live  when  utterly 
deprived  of  air.  Turtles  have  been  known  to  live  a 
month  and  more,  with  their  jaws  tied  closely  together 
and  stopped  up  with  sealing-wax.  Dr.  Edwards  com- 
pletely cut  out  the  lungs  from  two  frogs,  and  found  that 
one  lived  33  and  the  other  40  days,  in  wet  sand. 

Emily. — I  have  read  of  toads  being  found  alive,  com- 
pletely immured  in  solid  rocks,  or  in  the  heart  of  trees. 
My  faith  has  been  always  staggered  by  such  stories,  but, 
I  suppose  now  there  is  some  foundation  for  them  in  truth. 

Dr.  B. — It  is  probable  that  in  all  these  cases,  the  an- 
imals were  either  in  a  torpid  condition,  or  that  they  had 
communication  with  the  air  by  means  of  some' hole  or 
fissure  in  the  rock. 

In  the  Mollusca  or  shell-fishes,  we  find  considerable 
variety  in  the  construction  of  the  respiratory  organs.  In 
those  which  live  on  the  land,  and  those  which  are  obliged 
to  come  to  the  surface  of  the  water  to  breathe  the  air, 
we  observe  a  lung  which  differs  from  other  lungs,  by 
consisting  of  a  single  membranous  bag,  communicating 
externally  by  a  narrow  aperture  which  can  be  closed  or 
opened  at  the  will  of  the  animal,  while  the  bag  contract- 
ing and  dilating,  expels  or  admits  the  air.  On  the  sides 
of  this  cavity  are  ramified  an  almost  infinite  net-work  of 
blood-vessels,  containing  the  blood  which  is  to  be  reno- 
vated by  the  influence  of  the  air.  In  other  species,  we 
observe  gills  projecting  externally,  and  sometimes  re- 
sembling tufts  of  branches,  forming  a  kind  of  hedge  all 
around  the  body.  In  others,  the  gills  are  contained  in 
the  mantle  which  surrounds  their  body,  and  the  water  is 
admitted  and  expelled  by  the  successive  contraction  and 
dilatation  of  this  mantle. 

The  heat  of  the  Mollusca  is  very  nearly  the  same  as 
that  of  the  surrounding  medium;  in  the  snails  it  is  a  few 
degrees  above.  Mr.  Hunter  found  the  lungs  of  a  sndl 


RESPIRATION    OF    INSECTS.  115 

to  be  38°,  when  the  atmosphere  was  34°  ;  and  in  sev- 
eral instances,  when  the  temperature  of  the  air  was  30°, 
that  of  the  snails  was  considerably  above — 6  or  7°. 

In  Insects,  respiration  is  managed  differently  from 
what  it  is  in  either  of  the  classes  I  have  already  named. 
They  have  neither  lungs  nor  gills,  but  are  furnished  with 
minute  organs,  called  by  naturalists  stigmata,  which  are 
a  number  of  small  tubercules,  ranged  along  each  side 
oi  the  body,  each  having  an  aperture  at  the  top,  called 
the  spiracle,  through  which  the  air  enters.  These  stig- 
mata are  situated  on  the  sides  of  the  back,  and  lead  into 
true  air-tubes,  which  branch  off  in  every  direction,  sup- 
plying all  the  parts  of  the  body  and  members  with  air. 
That  these  are  respiratory  organs,  there  can  be  no  doubt, 
for  if  they  be  covered  up  with  oil,  respiration  ceases, 
and  the  insect  dies.  If  they  be  stopped  up  on  one  side 
only,  the  vital  functions  of  that  side  are  impeded,  and 
the  members  are  paralyzed. 

Emily. — A  curious  kind  of  respiration  surely ;  and  a 
curious  kind  of  circulation  it  must  be  to  correspond  with 
it ;  for  I  have  not  the  slightest  conception  how  it  is  con- 
structed. 

Dr.  B. — A  true  circulation  never  has  been  discover- 
ed in  perfect  insects.  The  blood  is  collected  into  one 
large  vessel  situated  in  the  back,  but  no  vessels  have  been 
observed  branching  off  from  it.  The  air-tubes  seem  to 
serve  the  office  of  blood-vessels,  and  present  a  singular 
contrast  to  those  of  the  higher  animals.  In  them  the 
blood  is  carried  to  the  air  ;  in  the  insects,  the  air  is  car- 
ried to  the  blood — or  as  Cuvier  beautifully  expresses  it, 
"  the  air  goes  in  search  of  the  blood." 

The  respiratory  organs  of  some  larva  of  insects, 
though  they  live  in  water,  are  fitted  for  breathing 
only  air.  They  are  situated  in  one  extremity  of  the  crea- 
ture in  a  tail-like  appendage  which  they  always  contrive 
to  keep  above  the  surface,  for  if  plunged  entirely  be- 
neath, they  appear  restless  and  agitated,  making  fre- 
quent attempts  to  rise  again  to  the  air.  Some  of  them 


116  SECRETION. 

are  capable  of  extending  their  tails  to  a  considerable  de- 
gree, so  that  they  can  keep  them  above  the  surface 
without  always  changing  their  positions  with  every 
change  in  the  level  of  the  water.  Reaurner  desirous  of 
seeing  how  far  they  could  thus  extend  themselves,  be- 
gan to  add  water  slowly  till  he  had  raised  it  six  inches ; 
the  larvae  in  the  mean  time  continued  to  lengthen  them- 
selves until  they  reached  this  height,  when  they  were 
forced  to  change  their  position  and  attach  themselves 
high  up  on  the  sides  of  the  vessel. 

Spiders  breathe  by  means  of  eight  or  ten  stigmata 
which  lead  into  a  sac,  on  the  sides  of  which  are  situated 
little  laminae  or  fringes,  in  which  the  blood  circulates 
that  is  to  be  renewed  by  the  air. 

Leeches  and  earth-worms  have  no  other  apparatus 
for  breathing  but  the  skin,  in  the  vessels  of  which  the 
blood  is  aerated. 

Emily. — What  wonderful  diversity  in  the  construction 
and  arrangement  of  organs,  whose  ultimate  purpose  is 
the  same  !  And  how  perfectly  does  every  change  har- 
monize with  other  co-existing  modifications  ! 

Dr.  B. — Having  finished  the  subject  of  respiration, 
we  will  turn  our  attention  to  the  function  of  secretion. 

Emily. — Secretion  means  separation ;  I  had  no 
idea  that  there  was  any  such  function  as  this  in  the  ani- 
mal economy. 

Dr.  B. — All  the  fluids  in  the  animal  body  are  de- 
rived from  the  blood,  and  the  process  by  which  they 
are  separated  from  the  blood  is  called  secretion.  But 
you  are  not  to  suppose  that  all  these  fluids  existed 
already  formed  in  the  blood,  and  that  the  only  object  of 
secretion  is  to  separate  them  therefrom  ;  for  some  of 
them — in  deed  most  of  them — are  formed  by  the  se- 
cretory organs  from  materials  which  exist  uncombined 
with  the  blood. 

Emily. — This  process  approaches  the  operations  of 
chemistry  nearer  than  any  other  which  we  have  yet  at- 
tended to. 


AQUEOUS    SECBET10NS.  lit 

Dr.  B. — And  yet  it  is  no  easier  to  explain  it  on  any 
chemical  principles,  with  which  we  are  acquainted,  than 
the  other  functions  of  life.  They  all  indeed  are  govern- 
ed by  laws  apparently  chemical,  and  to  such  a  degree  as 
to  justify  the  language  of  a  very  distinguished  French 
physician,  who  has  styled  them  a  "  vital  chemistry."  Of 
the  precise  manner  in  which  this  function  is  performed 
we  are  totally  ignorant. 

Emily. — But  what  is  the  nature  of  the  secretory  or- 
gans ?  Cannot  we  obtain  some  light  from  this  source  ? 

Dr.  B. — Not  the  least.  We  here  feel  the  full  force 
of  a  truth  recognized  by  anatomists,  that  the  most  per- 
fect knowledge  of  the  structure  of  a  part  does  not  nec- 
essarily lead  us  to  a  knowledge  of  its  function.  The  or- 
gans of  secretion  are  so  varied  in  their  form  and  struc- 
ture, that  it  is  difficult  to  exhibit  a  correct  general  view 
of  them,  and  an  idea  of  their  details  can  be  obtained  on- 
ly by  personal  examination.  They  are  called  glands  ; 
they  vary  in  size  from  that  of  a  pin's  head  to  the  magni- 
tude of  the  largest  organs  in  the  body  and  are  generally 
of  a  rounded  shape.  They  consist  of  a  multitude  of  mi- 
nute arteries  and  veins  connected  by  means  of  cellular 
substance.  The  fluid  which  is  secreted  from  the  blood 
in  these  vessels,  is  either  taken  up  and  carried  away  to 
fulfil  its  destined  purpose,  by  other  vessels,  or  more 
properly  ducts  ;  or  the  fluid  is  poured  out  directly  as  fast 
as  it  is  secreted,  on  the  surface  of  the  parts  where  the 
glands  are  placed,  without  the  intervention  of  any  duct. 
To  obtain  a  clearer  jdea  of  the  secretions,  we  will  dis- 
tinguish them  into  the  five  following  classes,  viz :  the 
aqueous,  the  serous,  the  mucous,  the  oleaginous,  and  the 
resinous , 

Emily.— -And  all  these  are  derived  from  one  and  the 
same  source — the  blood.  What  an  immense  storehouse 
of  heterogeneous  materials,  this  fluid  must  be  ! 

Dr.  B. — We  have  not  time  to  say  much  about  them, 
and  therefore,  shall  barely  say  enough  to  give  you  some 
idea  of  their  nature  and  use.  The  aqueous  consists  al- 


118  SEROUS    SECRETIONS. 

most  wholly  of  water.  The  principal  one  of  them  is  the 
matter  of  perspiration  secreted  from  the  skin,  and  though 
almost  entirely  composed  of  water,  its  expulsion  from 
the  system  is  absolutely  necessary  to  a  state  of  good 
health.  Its  quantity  is  so  small  that  it  is  always  imper- 
ceptible to  the  eye,  unless  it  be  increased  by  an  unusual 
warmth  of  the  body.  Then  it  collects  in  large  drops  on 
the  skin,  and  is  popularly  called  sweat.  It  has  been  as- 
certained from  experiment,  that  the  whole  quantity  of 
insensible  perspiration,  including  that  from  the  lungs,  va- 
ries from  eleven  to  thirty-two  grains  in  a  minute. 

Emily. — I  never  knew  before,  that  the  lungs  perspi- 
red ;  pray  how  is  that  fact  ascertained  ? 

Dr.  B. — You  have  only  to  look  at  a  person  in  a  cold 
day,  when  he  is  pouring  out  from  mouth  and  nose  suc- 
cessive jets  of  warm  vapour,  which  is  condensed  by  the 
cold  air,  to  satisfy  yourself  of  the  fact ;  or  to  save  the 
trouble  of  going  out  on  purpose,  just  breathe  a  few  times 
on  the  mirror,  and  see  the  matter  of  perspiration  con- 
densed on  its  cold  surface. 

Emily. — I  have  observed  all  this,  but  I  never  imagined 
it  came  from  the  lungs. 

Dr.  B. — A  curious  fact  in  the  animal  economy  is, 
the  nice  sympathy  which  exists  between  the  lungs  and 
the  skin.  Hence,  in  a  climate  where  the  temperature 
is  constantly  undergoing  great  and  sudden  changes,  you 
see  a  fruitful  source  of  disease.  The  perspiration  of  the 
skin  is  frequently  checked — the  irritation  is  propagated 
by  sympathy  to  the  lungs — these  delicate  organs  are 
stimulated  beyond  their  natural  measure  by  the  increased 
action  to  which  they  are  thus  subjected — -frequent  repi- 
tition  of  this  undue  excitement  leads  to  inflammation  and 
change  of  structure — and  consumption  is  the  common 
termination  of  the  scene. 

The  serous  secretions  do  not  differ  materially  from 
the  serum  of  the  blood,  and  are  poured  out  over  the 
whole  surface  of  the  serous  membranes.  These  mem- 
branes line  the  cavities  of  the  body  which  have  no  com- 


RESINOUS    SECRETIONS.  119 

rnunication  with  the  atmosphere,  such  as  the  abdomen, 
thorax,  pericardium,  pleura,  &tc.,  and  are  reflected  over 
the  organs  which  lie  in  these  cavities.  The  principal 
use  of  these  secretions  is,  to  furnish  these  parts  with  a 
proper  degree  o£  moisture,  so  that  they  may  glide  freely 
and  smoothly  over  one  another.  In  diseased  states  of  the 
body,  these  secretions  sometimes  accumulate  to  a  pro- 
digious extent,  constituting  the  disease  of  dropsy. 

The  mucous  secretions  are  a  transparent  viscid  fluid, 
of  a  saltish  taste,  consisting  of  water  and  a  very  small 
portion  of  several  alkaline  and  earthy  salts.  It  is  poured 
out  from  the  surface  of  those  membranes  whtfh  line 
cavities  of  the  body  that  have  an  external  communica- 
tion, as  the  alimentary  canal,  air-passages,  &.C.,  serving 
to  protect  these  parts  from  the  atmosphere,  and  concur- 
ring by  means  of  its  peculiar  properties,  in  the  perform- 
ance of  their  functions.  It  is  formed  by  minute  bodies 
of  a  glandular  character,  immediately  below  the  mem- 
brane called  mucous  crypto  ;  sometimes  however,  it  is  se- 
creted from  glands  of  a  considerable  size,  as  the  parotid 
and  salivary  glands  in  the  mouth,  which  secrete  the 
saliva. 

Of  the  oleaginous,  the  principal  is  the  fat  which  is 
found  in  different  parts  of  the  body,  and  always  secreted 
from  the  cellular  tissue.  Its  chief  use  seems  to  be  the 
protection  that  it  gives  to  the  parts  where  it  exists,  against 
the  pressure  of  foreign  bodies,  as  in  the  sole  of  the  foot 
for  instance,  and  to  give  a  general  rotundity  of  outline 
to  -the  surface.  In  some  cases,  as  in  corpulency,  it  ac- 
cumulates without  answering  any  particular  purpose ; 
here  the  object  of  th/  secretion  seems  to  be  merely  to 
free  the  blood  from  its  superfluous  carbon  and  hydro- 
gen. The  milk  of  animals  belongs  to  this  class  of  secre- 
tions. 

The  resinous  secretions  consist  of  substances  very  re- 
mote from  any  thing  we  find  in  the  blood.  The  princi- 
pal of  them  is  the  bile  which  has  been  already  described. 
It  is  called  a  resinous  secretion,  because  it  contains  a 


120          SECRETION    IN    THE    INFERIOR    ANIMALS. 

peculiar  substance,  called  picromel,  or  the  resin  of  the 
bile. 

Emily. — Does  this  function  in  the  inferior  animals 
vary  as  much  as  respiration,  circulation,  &c.  ?  I  hope 
you  will  not  confine  your  view  of  it  to  man  alone,  for  to 
me  the  history  of  the  vital  functions  as  they  exist  in  the 
inferior  animals,  is  no  less  interesting. 

Dr.  B. — The  function  is  probably  performed  in  the 
same  way  in  them  that  it  is  in  man ;  its  products  how- 
ever are  varied  almost  to  infinity.  As  it  would  be  for- 
eign to  our  purpose  to  take  them  up  in  detail,  we  must 
be  content  with  looking  only  at  a  few  of  the  most  impor- 
tant and  curious.  A  singular  product  of  secretion  in  the 
mammiferous  class,  are  the  horns  of  the  ruminating  ani- 
mals. In  the  winter  or  spring  season,  an  unusual  quan- 
tity of  blood  is  determined  to  the  head,  a  membrane  is 
formed  on  the  skull  containing  numerous  vessels,  bony 
matter  is  secreted  from  them,  and  the  membrane  extends 
until  the  whole  horn  is  produced.  In  some  families  this 
process  is  performed  annually — the  horns  being  shed 
once  a  year. 

The  venom  of  serpents  is  also  a  product  of  secretion. 
The  venomous  serpents  are  provided  with  a  couple  of 
long  fangs,  which  they  have  the  power  of  erecting  and 
depressing  at  will.  At  the  bottom  of  the  fang  is  a  little 
gland  that  secretes  the  poison,  and  a  canal  in  the  middle 
of  the  fang  gives  issue  to  the  venom  when  required. 
The  shells  of  the  shell-fishes — those  beautiful  shells 
whose  brilliant  and  variegated  colors  you  have  so  often 
admired,  are  secreted  from  the  membrane  that  forms 
the  envelope  of  the  animal.  What  is  still  more  strange, 
those  branches  of  coral,  sea-fans  which  you  have  fre- 
quently seen,  are  secreted  by  animals  of  microscopical 
dimensions. 

Emily. — Indeed.  Dr.  B.,  I  have  been  told  that  the 
coral  itself  is  of  an  animal  nature,  and  have  been  rallied 
not  a  little  for  expressing  my  incredulity  about  the  fact, 
for  it  always  appeared  to  be  nothing  but  limestone. 


SECRETION 


INSECTS* 


l)r.  B.  —  You  have  either  been  misinformed,  or  have 
^misunderstood  your  informants.  The  coral  is  the  pro- 
duce of  animals  of  the  Zoophyte  class,  and  is  raised  ior 
the  purpose  of  serving  as  an  abode  for  myriads  of  these 
minute  creatures  who  extend  their  feelers  through  the 
apertures  which  you  may  observe  on  the  surface.  So 
numerous  are  these  beings  and  so  rapidly  do  they  carry 
on  the  construction  of  their  habitations,  that  whole  moun- 
tains of  coral  are  sometimes  formed  under  the  sea,  en- 
circling islands  and  coasts,  and  filling  the  path  of  the 
navigator  with  unknown  perils.  Some  of  the  islands  in 
the  Pacific  ocean  are  formed  entirely  in  this  way. 

Emily.  —  Well>  this  is  the  most  astonishing  of  all; 
whole  islands  tiie  produce  of  secretion  !  and  that  too,  of 
creatures  which  are  hardly  perceptible  to  the  naked  eye  ! 
I  thought  you  had  already  mentioned  some  most  won- 
derful facts,  but  really  this  surpasses  them  all. 

Dr.  B.—  Perhaps  you  would  be  equally  surprised  if 
[  should  tell  you  that  the  very  garment  which  you  wear, 
is  the  product  of  secretion  ;  and  yet  such  is  the  case. 

Emily.  —  Do  explain  yourself,  Dr.  B.,  unless  you  are 
really  jesting  I  do  not  understand  it.  This  silk  frock  of 
mine,  I  had  always  imagined,  was  woven  in  looms  in 
foreign  countries  ;  can  it  be  this  you  refer  to  ? 

Dr.  5.—  Right  ;  but  the  silk  itself  once  constituted 
the  cocoon  or  habitation  of  an  insect,  which  it  made  for 
itself  to  pass  away  the  period  in,  which  intervenes  during 
its  change  from  the  larva  to  the  perfect  state.  It  is  spun 
by  the  silk-worm,  from  materials  that  are  abundantly 
furnished  by  certain  secretory  organs,  expressly  destined 
for  this  purpose,  and  afterwards  is  woven  by  manufactu- 
rers into  a  stuff  which  has  become  indispensable  in  all 
civilized  countries.  This  must  finish  the  subject  of  se- 
cretion, and  if  you  are  not  wearied  we  will  proceed  to 
examine  another  of  the  functions  of  life. 

Emily.  —  Have  no  concern  on  that  score.  But  pray, 
what  may  be  the  next  subject  that  will  require  our  at- 
tention ? 

11 


VENOM    OF     SERPENTS. 


Dr.  B.  —  We  are  now  to  consider  a  very  important, 
though  rather  obscure  function  —  that  of  absorption,  by 
which  different  substances,  within  or  without  the  body, 
are  taken  into  the  circulation,  and  appropriated  to  vari- 
ous purposes.  This  function  is  very  manifest  on  the 
skin,  though  not  so  active  here  as  in  some  other  parts. 
Thus,  if  mercurial  ointment  be  rubbed  on  but  a  small  por- 
tion of  the  surface,  for  a  sufficient  length  of  time,  it  will 
finally  affect  the  whole  constitution.  It  is  by  absorption 
that  the  poisonous  matter  of  contagious  diseases,  such  as 
small  pox,  measles,  &c.  is  admitted  into  the  system  and 
produces  a  similar  affection. 

Emily.  —  The  poison  of  the  venemous  serpents,  I  sup- 
pose, is  introduced  into  the  circulation  in  the  same  way. 

Dr.  B.  —  Not  precisely  the  same  ;  it  is  absorbed  by 
the  skin  indeed,  but  it  is  necessary  thatthe  surface  should 
be  broken,  as  it  is  by  the  tooth  of  the  animal,  —  merely 
rubbing  it  on  the  sound  skin  would  produce  no  injurious 
effects.  1  suppose  now  you  see  at  once  the  utility  of 
applying  cupping-glasses,  over  the  wound  and  ligatures 
above  it,  as  well  as  the  practice  sometimes  observed  of 
sucking  the  wound  with  the  mouth. 

Emily.  —  I  should  think  that  the  circulation  in  the  part 
being  partially  stopped  by  these  means,  the  absorption 
of  the  morbific  matter  is  checked,  and  extracted  from 
it  by  the  latter  methpd.  But  is  it  not  liable  to  be 
absorbed  from  the  mouth  of  the  person  who  sucks  the 
wound  ? 

Dr.  B.  —  Not  if  the  surface  of  the  living  membrane  be 
sound. 

Emily.  —  Still  is  there  no  danger  of  swallowing  some 
of  it  along  with  our  saliva  ?  I  am  sure  I  never  should 
dare  to  do  it,  from  this  apprehension. 

Dr.  B.  —  The  lining  membrane  of  the  stomach  you 
know,  is  merely  a  continuation  of  that  in  the  mouth, 
and  swallowing  the  poisonous  matter  would  be  equally 
harmless  with  holding  it  in  the  mouth.  The  poison  oi 
vipers  has  been  swallowed  without  giving  rise  to  any  im~ 


ABSORPTION.  123 

pleasant  effects,  and  in  our  new  settlements,  swine  are 
said  to  devour  rattlesnakes,  and  with  a  high  relish  too  for 
the  choice  morsel.  But  absorption  not  only  takes  up 
foreign  substances,  but  is  in  incessant  action  in  every 
part  of  the  system,  removing  particles  of  matter  that  are 
no  longer  fit  for  the  purposes  of  the  vital  economy,  and 
whose  places  are  supplied  by  fresh  materials,  as  well  as 
others  that  have  accumulated  in  particular  parts,  as  a 
consequence  of  injury  or  disease.  Thus  the  mucous  and 
serous  secretions  are  constantly  absorbed  just  as  fast  as 
they  are  secreted.  If  this  were  not  so,  they  would  ac- 
cumulate and  become  a  source  of  disease.  In  bruises 
and  swellings  where  blood  or  the  serous  portion  of  it  is 
eftused,  no  cure  can  take  place  until  these  fluids  are  re- 
moved, and  absorption  is  the  agent  by  which  this  is  ef- 
fected. 

Emily. — I  have  often  wondered  what  becomes  of  the 
blood  which  is  poured  out  when  a  bone  is  broken  or  a 
severe  bruise  received,  for  I  never  observed  that  in  such 
cases,  the  physician  used  any  means  to  take  it  away. 

Dr.  B. — It  is  because  he  is  acquainted  with  this  pow- 
er of  the  animal  economy^  and  knows  that  it  is  better  to 
forbear  offering  his  assistance.  You  may  set  this  down 
as  a  general  law  of  the  animal  economy,  that  when  the 
good  condition  of  the  system  no  longer  requires  the 
presence  of  any  part,  it  is  removed  forthwith  by  the  pow- 
ers of  absorption ;  provided  that  the  constitution  enjoys 
at  the  time  a  sufficient  degree  of  health  to  accomplish 
this  process. 

Emily. — I  believe  you  have  not  yet  mentioned  the 
organs  by  which  this  function  is  performed,  and  I  have 
just  thought  of  asking  the  question. 

Dr.  B. — This  has  lately  been  made  a  subject  of  con- 
siderable discussion,  and,  opinions  are  not  yet  settled 
concerning  it.  According  to  the  old  theory,  the  func- 
tion of  absorption  is  performed  by  a  set  of  vessels  very 
similar  to  that  by  which  the  chyle  is  absorbed  from  the 
alimentary  canal.  The  lymphatic  vessels,  as  they  are 


124  VENOUS    ABSORPTION. 

called,  exist  in  every  portion  of  the  body  ;  like  the  veins% 
they  diminish  in  number  as  they  increase  in  size,  while 
pursuing  their  course  towards  the  veins  of  the  arms  into 
which  they  pour  their  contents.  In  their  course  they 
frequently  traverse  the  lymphatic  glands,  which  are  to 
these  vessels  what  the  mesenteric  glands  are  to  the  lac- 
teals.  They  are  situated  chiefly  in  the  groin,  arm-pits, 
and  neck,  in  which  latter  place  they  are  frequently 
swollen  in  consequence  of  cold. 

Emily. — What  is  the  nature  of  the  fluids  contained 
in  the  lymphatic  vessels  ?  I  suppose  however,  since 
they  are  the  general  reservoir  of  all  the  waste  and  use- 
less portions  of  the  body,  that  their  contents  are  of  rather 
a  heterogeneous  character.  But  I  am  surprised  that 
they  should  be  poured  into  the  mass  of  blood,  since  be- 
ing entirely  useless,  I  should  suppose  they  would  find 
their  way  out  of  the  system  by  some  other  channel. 

fir.  B. — The  fluid  in  the  lymphatic  vessels  is  called 
lymph ;.  it  is  of  a  whitish  colour,  slightly  saline  in  taste, 
and  instead  of  being  composed  of  very  heterogeneous 
materials,  is  exceedingly  simple  in  its  composition. 
These  and  many  other  facts  lately  led  physiologists  to 
the  conclusion,  that  these  vessels  could  not  be  the  sole 
agents  of  absorption,  as  was  generally  supposed  after 
they  were  discovered.  The  suggestion  was  often  made 
that  the  veins  had  some  share  in  this  function,  but  it  was 
never  satisfactorily  demonstrated  to  be  so,  till  Majendie, 
a  few  years  ago,  published  the  results  of  his  interesting 
experiments. 

Emily.-r^&o,  Dr.  B.,  relate  some  of  them,  for  I  am 
desirous  to  know  on  what  reasons  the  lymphatics  have 
been  excluded  from  the  absorbent  function,  and  on  what 
ground  rests  the  doctrine  of  venous  absorption,  as  Ma- 
jendie's  must  be  called. 

2)r>  J5. — One  or  two  of  the  most  striking  I  will  re- 
late. Majendie  having  opened  the  body  of  a  dog,  put 
two  ligatures  around  a  portion  of  the  intestinal  canal  at 
a.  short  distance  from  one  another,  thus  insulating  it  com- 


.NUTRITION. 

pietely  from  the  rest.  Up  next  divided  with  great  care 
all  the  chyliferous  and  lymphatic  vessels,  the  veins  and 
arteries  leading  to  it  with  the  exception  of  one  artery 
and  one  vein,,  and  then  divided  above  and  below  the 
ligature,  so  that  if  remained  connected  to  the  body  only 
by  one  artery  and  one  vein.  He  then  injected  into  it  a 
decoction  of  a  certain  poisonous  substance,  and  in  six 
minutes,  it  manifested  its  poisonous  effects  on  the  con- 
stitution. A  pupil  of  his  afterward  varied  the  experiment 
by  leaving  the  portion  of  intestine  connected  to  the  body 
only  by  the  chyliferous  vessels,  instead  of  an  artery  and 
vein.  A  similar  injection  being  thrown  into  it,  the  pois- 
oning did  not  take  place,  even  at  the  end  of  half  an 
hour  ;  but  when  one  of  the  veins  was  freed  which  had 
been  tied  but  not  divided,  the  poisoning,  took  place  im- 
mediately. These  experiments  have  since  been  verified 
by  other  physiologists,  particularly  Messrs.  Lawrence 
and  Coates  of  Philadelphia. 

Emily. — Most  ingenious  and  satisfactory  experiments 
surely — conclusive,  I  should  suppose  in  favor  of  the 
doctrine  of  venous  absorption.  But  what  then  are  we 
to  do  with  the  lymphatics  ?  We  must  find  some  use 
for  them.. 

Dr.  B. — If  we  deny  the  power  of  absorption  to  the 
lymphatics,  their  functions  become  a  matter  of  great  ob- 
scurity. It  has  been  suggested — and  this  is  the  most 
probable  suggestion  that,  has  yet  been  offered — that  the 
lymph  is  a  highly  animaiized  fluid  destined  for  important 
purposes  ;  farther  than  this  we  know  very  little. 

The  functions  of  which  we  have  now  treated,  ara  to- 
be  considered  as  only  preparatory  processes  for  the  last 
and  most  important  of  all,  nutrition — the  seat  of  which 
is  in  every  part  of  the  body.  The  particles  of  our  food 
after  having  undergone  those  diversified  operations  which 
you  have  heard  related,  at  last  become  incorporated 
with  the  materials,  and  form  constituent  -parts  of  the 
body  itself,  After  a  time  they  lose  those  properties 
;vhj.ch  fitted  them  for  this  purpose,  they  are  taken  awav, 
11* 


126  NUTRITION. 

carried  out  of  the  system,  and*  new  ones  are  deposited 
to  supply  their  place. 

Emily. — Amidst  such  a  multitude  of  operations,  how 
is  it  possible  that  no  clashing,  no  interference  should 
take  place — that  the  system  should  not  be  destroyed  by 
the  action  of  its  own  organs  ! 

Dr.  B. — See  too,  amidst  all  this  simultaneous  reno- 
vation and  decay,  how  admirably  the  forms  and  beauty 
of  the  organs  are-  preserved  !  Even  the  most  delicate 
lineaments  of  the  face,  and  that  intelligent  lustre  of  the 
eye,  which  are  recognized  by  all,  but  defy  the  power  of 
the  master-artist  to  embody  on  the  canvass  or  the  mar- 
ble, are  retained  with  striking  distinctness  through  the 
various  stages  of  life. 

Emily. — Can  you  inform  me  how  long  any  particle 
continues  a  constituent  portion  of  the  body  ?  If  they 
are  constantly  changing  in  this  manner  from  birth  till 
death,  why  certainly  at  different  periods  of  life,  we  must 
be  very  different  persons,  and  we  may  justly  I  ihink, 
apprehend  the  loss  of  our  personal  identity. 

Dr.  B. — Physiologists,  I  believe,  have  never  yet 
been  able  to  find  an  answer  to  your  question.  Howev- 
er, you  have  nothing  to  fear  on  the  score  of  your  per- 
sonal identity,  for  this  consists  not  so  much  in  the  mat- 
ter which  composes  our  bodies,  as  in  the  forms  which  it 
assumes,  and  the  spirit  by  which  it  is  actuated. 

Emily. — Does  riot  the  activity  of  nutrition  vary  in  the 
different  periods  of  life  ?  It  seems  rational  to  suppose 
that  it  would  correspond  with  the  energy  of  the  consti- 
tution generally. 

Dr.  B. — Your  conjecture  is  correct ;  nutrition  enjoys 
its  greatest  activity  in  infancy  and  childhood,  when  the 
body  is  not  only  to  be  nourished  simply,  but  increased 
and'  developed.  It  is  then  that  the  features  are  most 
liable  to  alteration  ;  that  wounds  are  more  readily  healed; 
and  fractures  o£tbe  bones  most  speedily  united. 

Emily. — At  what  precise  period  in  all  the  varied  op- 
Aerations  to  which  the  food  is  subjected,  does  it  undergo. 


NUTRITION.  12T 

that  change  which  fits  it  -for  the  purpose  of  nutrition  r 
converts  if  from  dead  matter  into  organized  living  parti- 
cles ?  Or  is  this  change  wrought  gradually  ? 

Dr.  B. — In  all  probability,  this  change  is  not  effected 
at  any  particular  stage  in  the  route  which  the  aliment 
pursues,  but  is  accomplished  gradually  by  the  various 
processes  to  which  it  is  subjected  before  it  reaches  its 
ultimate  destiny.  When  fully  and  perfectly  animalized, 
it  furnishes  the  materials  whence  all  the  parts  of  the  body 
whatever  may  be  their  nature  or  situation,  are  to  receive 
their  supplies.  From  the  vessels  which  circulate  in  the 
bones,  bony  matter  is  deposited ;  in  the  liver,  it  is  bile ; 
in  the  salivary  glands,  it  is  saliva,  &c. 

Emily. — Again  I  must  express  my  surprise,  that  amidst 
this  great  variety  of  chemical  changes,  this  play  of  innu- 
merable affinities,  there  is  nothing  of  interference  or  con- 
fusion. How  wonderful  !  how  mysterious  ! 

Dr.  B. — To  heighten  the  mystery  still  more,  we  find 
substances  not  contained  in  the  blood,  and  which,  chem- 
istry, having  gone  to  the  utmost  limits  of  analysis,  has 
been  contented  to  call  simple  bodies.  The  uniform 
composition  of  animals  is  also  an  exceedingly  strange 
fact.  The  flesh  and  bones  of  a  sheep,  as  we  have  be- 
fore observed,  whose  diet  is  exclusively  vegetable  ;  of  a 
lion,  which  subsists  on  the  flesh  of  animals ;  and  of  a 
hog,  which  lives  upon  a  mixed  diet,  exhibit  the  same 
chemical  composition,  and  are  formed  by  processes 
which  chemistry  has  never  been  able  to  imitate.  As  but 
little  or  no  nitrogen  is  taken  into  the  system  in  respira- 
tion, it  is  inexplicable  how  this  substance  should  enter  as 
much  into  the  composition  of  herbivorous,  animals  in 
whose  food  only  a  small  quantity  of  nitrogen  exists,  as 
in  that  of  carnivorous  animals  in  whose  food  this  princi- 
ple greatly  abounds.  Lime  likewise,  is  found  in  the 
body  in  sometimes  double  the  quantity  of  what  is  con- 
tained in  the  food. 

Emily. — The  living  system  may  be  considered  I  think, 
a,  real  laboratory  which  enchains  our  admiration  at  the. 


NUTRITION. 

greatness,  the  extent  and  perfection  of  its  operations. 
They  are  truly  the  result  of  a  "  vital  chemistry,"  as  far 
beyond  the  reach  of  man's  imitation,  as  the  power  that 
formed  this  laboratory,  is  beyond  his  own. 

Dr.  B.—^We  have  now  finished  the  account  of  the 
organic  functions ;  in  our  next  conversation  we  shall 
beg^n  with  those  of  animal  life. 


NERVOUS    SYSTEM. 


CONVERSATION  VI. 


Nervous  system — its  progressive  developement  in  the  in- 
ferior animals — the  spinal  marrow — nerves — brain — 
functions  of  the  nervous  system — sensation — ^volition- — 
Mr.  Bell's  discoveries— theories  oj 'the  nervous  power — 
Dr.  Wilson  Philips'  experiments — phrenology — com- 
parison of  the  brain  of  man  and  those  of  the  inferior 
a nimals— facial  angle — instinct— reason . 

Dr.  B. — The  functions  of  organic  life— those  which 
we  have  examined — are  all  possessed  to  a  certain  degree 
by  vegetables,  as  well  as  animals.  But  the  latter  class 
of  beings,  and  particularly,  he  who  stands  at  the  head 
of  it — man,  enjoys  a  higher  and  nobler  state  of  existence. 
They  are  conscious  of  their  own  existence  and  of  the 
presence  of  things  around  them  ;  and  they  are  affected 
with  pleasure  or  pain v according  to  the  manner  in  which 
these  objects  affect  their  constitution.  For  the  enjoyment 
of  this  function,  they  are  indebted  to  a  complex  series  of 
organs  called  the  Nervous  System.  With  this  alone 
however,  they  would  have  remained  imperfect  beings, 
enjoying  an  existence  less  enviable  than  that  of  the  hum- 
blest vegetable.  Capable  of  receiving  impressions  from 
the  external  world,  the  power  of  acting  in  consequence 
of  these  impressions,  of  making  their  condition  change  as 
the  objects  around  them  change,  was  obviously  neces- 
sary to  complete  the  perfection  of  their  organization,  and 
the  harmony  of  relations  existing  between  them  and  the 


130      DEVELOPEMENT    OF    THE    NERVOUS    SYSTEM. 

genenal  system  of  nature.  To  accomplish  this  latter 
purpose,  we  are  provided  with  a  system  of  organs,  call- 
ed organs  of  locomotion. 

Emily. — Am  I  to  understand  that  the  latter  are  entire- 
ly subservient  to  the  former  organs — acting  only  when 
stimulated  by  them  ? 

Dr.  B. — Certainly  ;  no  voluntary  motion  takes  place 
without  the  action  of  the  nerves, — but  this  view  of  the 
subject  must  be  considered  at  another  time,  for  at  pre- 
sent we  must  look  at  the  structure  of  the  nervous  system. 
In  order  that  you  may  obtain  a  clearer  notion  of  this 
system,  we  will  first  examine  it  in  the  inferior  animals, 
and  thence  trace  it  up  into  the  nervous  system  of  man. 
In  this  manner,  you  will  see  in  a  very  interesting  light, 
its  gradual  developement,  and  the  relative  importance  of 
its  different  parts. 

Emily.— This  system,  like  the  others,  I  suppose,  is 
simple  in  the  lower  animals,  increases  in  complexity  as 
we  ascend  the  scale  of  being,  and  finally  exists  in  its  ut- 
most perfection  in  man. 

Dr.  B. — Yes — but  its  gradual  developement  differs 
from  that  of  the  other  organs,  in  one  very  remarkable 
point.  It  is-^-that  in  the  earliest  stages  of  existence,  it 
is  the  same  in  all ;  take  it. in  the  highest  state  of  perfec- 
tion in  which  it  is  observed,  and  we  find  that  before  it 
eould  attain  that  state,  it  had  to  pass  through  all  the  forms 
which  it  possessed  in  the  different  classes  of  inferior  an- 
imals in  their  perfect  state. 

J£mi1y> — If  I  understand  your  meaning  correctly,  the 
nervous  system  of  man,  before  it  attains  the  form  which 
we  behold,  has  first  presented  that  of  the  zoophytes, 
then  that  of  the  worms,  then  of  the  shell-fish,  then  of  the 
fishes,  and  so  on  through  the  whole  series. 

Dr.  B. — Precisely  so  ;  and  now  we  will  look  at  the 
proofs  of  this  doctrine.  In  the  lowest  orders  of  the 
Zoophytes,  the  only  trace  of  this  system  is  nothing  more 
than  nervous  molecules  unconnected  with  one  another, 
disseminated  through  the  substance  of  their  simple,  pulpy 


1>EVELOPEMENT    OF    THE    tfERVOUS    SYSTEM.       131 

structure.  In  Zoophytes  of  a  little  higher  organization, 
the  nervous  matter  appears  in  the  form  of  minute  and 
delicate  threads  arranged  around  the  principal  organs  of 
nutrition,  with  other  threads  proceeding  from  them  in  a 
radiated  mannef,  to  go  to  the'different  parts  of  the  body. 
In  the  next  orders  we  find  a  series  of  little  knots  of  ner- 
vous matter,  called  ganglia,  connected  by  two  nervous 
threads,  still  placed  around  the  organs  of  nutrition.  In 
the  earth  worm  belonging  to  a  still  higher  order,  the  ner- 
vous thread  is  single,  instead  of  double  as  before,  and 
the  ganglia  instead  of  appearing  independent  bodies,  are 
merely  swellings  of  this  thread,  from  which  proceed  sin- 
gle and  double  pairs  of  threads  alternately.  In  the  first 
orders  which  possess  senses,  we  find  the  anterior  ganglia 
enlarged  and  sending  out  filaments  to  supply  the  organs 
of  sense.  Thus,  as  the  organs  of  the  animals  increase, 
the  nervous  threads,  or  nerres  we  may  as  well  call  them, 
increase  in  number  and  perfection,  the  principal  mass 
still  being  placed  around  the  oesophagus.  In  the  fishes 
we  meet  for  the  first  time,  the  most  remarkable  modifi- 
cation which  the  system  undergoes.  The  main  nervous 
cord  becomes  enclosed  in  a  long  case  or  canal,  and  take 
the  name  of  spinal  marrow,  from  the  long  canal  which  is 
called  the  spine.  But  this  is  not  all :  at  the  summit  of 
the  spinal  marrow,  are  observed  several  large  ganglia 
connected  together  but  quite  distinct  from  one  another. 
This  constitutes  the  brain,  and  here  you  may  see 
it  in  this  cut.  In  the  brain  of  the  reptiles,  we  find 
an  addition  of  two  more  ganglia.  In  the  birds, 
these  last  ganglia  are  much  developed,  and  in  the 
mammiferous  tribes,  the  brain,  instead  of  being 
composed  of  separate  ganglia,  has  the  appearance 
of  a  single  organ,  whose  parts  are  no  longer  divi- 
sible into  distinct  bodies. 
Emily. — This  cut,  then,  according  to  your  theory, 
will  also  represent  the  brain  and  spinal  marrow  of  man, 
at  one  period  of  his  existence,  will  it  not  ? 


132 


THE    NERVES. 


Dr.  B. — Yes ;  and  to  be  perfectly  convinced  of  this 
fact,  you  have  only  to  compare  the  figure  of  the 
fishes'  brain  with  this  of  man's,  representing  the 
form  which  it  possesses  when  any  traces  of  or- 
ganization can  be  first  discerned. 

Emily. — -Well  this  is   strange  indeed  !   they 
seem  to  be   perfectly  alike  ;  at  least,  I  can  dis- 
cern no  essential  difference.     The  difference  be- 
tween them  however,   must  be  manifested  after- 
wards ;    this  being  the  permanent  form   of  the 
fishes'  brain,  while  in  man  it  is  only  temporary. 
Dr.  B. — It  is  succeeded  by  the  form  of  the  brain,  as 
it  appears  in   reptiles  ;  then  as   it  exists  in  birds ;  and 
finally  by    that  which  is  destined   to  be  its  permanent 
form. 

Emily. — But  you  also  said  that  in  the  lowest  classes, 
the  nerves  were  formed  before  the  spinal  marrow  and 
brain  showed  any  signs  of  existence, — now  is  this  ths 
case  too,  in  man  ? 

Dr.  B.^—Most  certainly  ;  the  nerves  may  be  seen 
quite  distinctly,  while  the  spinal  marrow  is  yet  in  a  semi- 
fluid state.  When  this  is  fully  organized,  the  nerves 
extend  themselves  to  its  sides,  and  join  it  by  two  divi- 
sions, called  the  anterior  and  posterior  roots.  This  figure 


will  give  you  a  little  better  idea  of  it,  than  you   can  ob~ 
tain  from  mere  verbal  description.     Here  you  see  the 


CHEMICAL    COMPOSITION    OF    THE    BRAIN.          133 

two  pairs  of  nerves  proceeding  towards  the   spinal  mar- 
row, one  on  each  side,  and  inserted  into  it  by  two  roots. 

Emily. — But  il  these  two  divisions  of  the  nerves,  have 
their  termination,  not  their  origin  in  the  spinal  marrow. 
is  it  not  improper  to  give  them  the  name  of  roots  % 

j}Tt  J5. — This  name  was  given  them  when  the  nerves 
were  supposed  to  originate  from  the  spinal .  marrow,  and 
is  now  retained  merely  for  the  sake  of  convenience. 

Emily. — Pray,  tell  me  how  many  nerves  go  to  the 
spinal  marrow  in  this  manner? 

Dr.  B. — The  whole  number  of  spinal  nerves  is  thir- 
ty-one on  each  side,  and  are  perfectly  regular  and  sym- 
metrical.— Tracing  the  spinal  marrow  upwards  into  the 
head,  we  find  it  terminated  by  the  oblong  marrow,  as 
a  column  is  surmounted  by  its  capital.  Nearly  all  the 
rest  of  the  brain  is  distinguished  into  two  portions,  the 
cerebellum,  occupying  the  inferior  and  posterior  parts  of 
the  head ;  and  the  cerebrum,  which  fills  up  the  remain- 
ing space.  Inclosed  in  its  bony  case,  and  enveloped  by- 
thick  membranes,  this  delicate  organ  has  all  the  securi- 
ty and  protection,  which  its  pre-eminent  importance  de- 
mands. The  quantity  of  blood  which  it  receives  is  re- 
markably large,  for  though  it  does  not  weigh  more  than 
one-fortieth  of  the  whole  body,  it  is  estimated  that  one- 
tenth  of  all  the  blood  sent  from  the  heart,  goes  to  this 
organ.  Its  external  portions  are  convoluted  in  structure, 
and  the  whole  has  a  soft,  pulpy  consistence. 

Emily. — Has  its  chemical  composition  ever  been  as- 
certained ?  I  feel  not  a  little  curious  to  know  "  what 
stuff  our  brains  are  made  of." 

Dr.  B. — It  has  been  found  that  about  three-fourths  of 
its  weight  is  water,  and  in  the  solid  parts  are  considera- 
ble fat,  a  peculiar  animal  principle,  called  ozmazome,  a 
quantity  of  albumen,  a  minute  portion  of  phosphorus, 
and  some  salts,  chiefly  phosphates  of  lime,  soda  and  am- 
monia. 

Emily. — Fat,  phosphorus,  lime  and  soda  !  Of  all  the 
strange  facts  which  you  have  related,  this  seems  to  be 
12 


134 


SPINAL  COLUMN. 


strangest.  Who  would  suppose  these  to  be  the  materials 
which  form  the  noble  organ  of  thought !  Does  the  brain, 
like  the  spinal  marrow,  receive  nerves  from  other  parts? 
Dr.  B. — Yes  ;  we  find  eleven  pairs  of  nerves  con- 
nected with  the  base  of  the  brain,  which  supply  the  or- 
gans of  sense,  the  muscles  of  the  face,  and  the  muscles 
concerned  in  respiration.  Coming  from  these  parts, 
they  pass  through  holes  in  the  bony  case  of  the  brain, 
and  run  along  its  base,  till  they  are  finally  lost  in  the  ob- 
long marrow. 

Emily. — You  observed  just  now,  that  the  spinal  mar- 
row is  enclosed  in  a  bony  case — the  spine  or  back  bone, 
I  believe.  I  do  not  clearly  perceive  how  this  can  be,  for 
I  thought  that  the  spine  was  solid  bone. 

Dr.  B. — I  will  describe  it  then,  a  little  more  definite- 
ly. The  back-bone,  spine,  spinal  column,  vertebral  co- 
lumn— for  it  is  designated  by  all  these  names — is  not 
formed  by  a  single  bone,  but  by 
twenty  four  small  bones  piled  upon 
each  other.  Each  bone,  as  you 
will  see  by  this  figure,  is  composed 
of  its  body  and  processes  ;  the  first 
is  thick,  nearly  cylindrical  in  shape, 
and  its  broad  flat  terminating  surfa- 
ces connect  it  with  the  bones  above 
and  below.  The  processes  are  those 
smaller  portions  of  bones,  proceed- 
ing from  different  portions  of  the 
body  in  pairs.  Two  pairs  serve  to 
interlock  and  bind  firmly  together, 
each  bone  to  its  neighbour  ;  while  the  other  pair,  after 
proceeding  a  short  distance  from  the  posterior  portion  of 
the  body,  meet  at  an  acute  angle.  Now  when  the  bones 
are  applied  to  each  other,  the  space  thus  enclosed  by 
these  posterior  processes,  will  form  a  continuous  canal 
from  beginning  to  end. 

Emily. — -And  it  is  in  this  canal  then,  that  the  spinal 
marrow  is  lodged.  But  why  could  not  the  spine  have 


FUNCTIONS  OF  THE  NERVOUS  POWER.       ,        135 

been  formed  by  one  single  bone  ?  I  cannot  possibly  con- 
ceive what  is  the  use  of  so  many  little  bones ;  I  should 
think  they  would  be  very  liable  to  be  displaced  amidst  all 
the  motions,  falls,  and  injuries  that  we  are  continually 
experiencing  in  a  greater  or  less  degree. 

Dr.  B. — If  the  spinal  column  were  formed  of  a  sin- 
le  bone,  the  whole  neck  and  body  would  be  complete- 
y  stiff  and  unyielding — admitting  motion  in  no  direction 
whatever.  In  order  to  admit  the  various  motions  of 
the  body,  some  flexibility  is  necessary  in  the  spine,  and 
this  can  be  obtained  only  by  forming  it  with  a  succes- 
sion of  several  small  bones,  united  together  sufficiently 
strong  to  allow  the  requisite  degree  of  motion,  without 
at  the  same  time  endangering  its  strength.  So  firmly 
are  they  united,  that  dislocations  are  the  rarest  of  all  in- 
juries. 

Emily. — My  proposition  was  indeed  absurd  ;  if  I  had 
thought  a  moment  longer  I  do'nt  believe  I  should  have 
appeared  so  stupid.  But  knowing  the  names  and  anat- 
omy of  these  parts,  Dr.  B.,  is  of  little  use  without  a 
knowledge  of  their  functions.  I  suppose  that  anato- 
mists who  have  examined  the  structure  and  develope- 
ment  of  this  system  with  so  much  perseverance,  have 
not  neglected  to  investigate  the  uses  of  its  several 
parts. 

Dr.  B. — Certainly  not ;  a  great  degree  of  research 
and  ingenuity  has  been  manifested  in  their  investiga- 
tions, and  tney  have  been  followed  by  some  very  inter- 
esting results.  The  functions  of  the  nervous  system 
have  been  reduced  to  two  classes  ;  the  nervous,  and  sen- 
sorial, — or  they  may  be  styled  two  distinct  powers  of 
the  nervous  system.  The  nervous  power  is  engaged  in 
the  performance  of  vital,  or  organic  actions ;  the  senso- 
rial  is  the  source  of  sensation,  volition,  intellect. 

The  most  important  functions  of  the  nervous  power, 
are  those  by  which  our  relations  with  the  external  world 
are  maintained.  Impressions  made  upon  the  organs  of 
sense,  are  transmitted  by  the  nerves  to  the  brain,  and 


13C          FUNCTIONS    OF    THE    NERVOUS    POWER. 

there,  by  means  of  the  sensorial  power,  are  recognised 
by  the  mind,  or  to  use  the  popular  phraseology,  become 
sensations. 

Emily. — But  how  is  it  known  so  certainly  that  the 
impression  is  conveyed  to  the  brain  by  the  nerve  solely  ? 
I  should  like  to  be  acquainted  with  the  grounds  of  this 
doctrine. 

Dr.  JB. — It  is  demonstrated  by  the  fact  abundantly 
established  by  experiment  and  observation,  that  if  the 
nerve  be  injured,  no  sensation  is  produced  in  the  mind. 
If  the  optic  nerve,  by  which  impressions  made  on  the 
organs  of  vision  are  communicated  to  the  brain,  be  in- 
jured in  any  way,  no  object  will  be  perceived,  though 
its  image  may  fall  on  the  retina  just  as  distinctly  as  be- 
fore. 

Emily. — I  do  not  perfectly  understand  how  sensa- 
tions are  experienced  in  the  brain ;  I  have  always  con- 
sidered their  seat  to  be  in  the  extremities  of  the  nerves, 
or  the  organs  of  sense  themselves.  Surely,  if  I  grasp  a 
warm  body  with  my  hand,  I  feel  the  warmth  in  my  fin- 
gers, not  in  my  brain ;  if  a  wound  be  made  in  my  arm, 
I  feel  the  pain  in  the  wound,  not  in  the  brain. 

Dr.  B. — There  is  a  very  obvious  distinction  be- 
tween sensations  and  impressions  ;  the  latter  are  the 
changes  produced  in  the  extremities  of  the  nerve ;  the 
former,  the  changes  produced  in  the  brain  and  commu- 
nicated to  the  mind.  The  mind  however,  is  accusto- 
med to  refer  the  seat  of  its  sensations  to  the  seat  of  the 
impressions,  which  circumstance  must  be  borne  in  mind, 
or  we  shall  fall  into  an  error.  But  we  are  anticipating 
this  part  of  our  subject,  for  sensation  is  an  effect  of  the 
sensorial  power,  and  we  have  not  yet  finished  our  ex- 
amination of  the  nervous  power. 

Another  function  of  the  nervous  power  is  to  transmit 
to  the  voluntary  muscles  the  stimulus  necessary  for  their 
action.  When  I  wish  to  grasp  the  object  before  me, 
the  muscles  must  receive  their  proper  stimulus  before 
they  can  be  put  into  action.  This  is  conveyed  .from  the 


DISCOVERIES  OF  MR.  BELL.  137 

brain,  along  the  nerves,  to  the  parts  to  be  affected,  and 
-may  be  called  the  stimulus  of  volition. 

Emily.— Is  this  function  also  demonstrated  by  expe- 
riment, like  the  last  ? 

£)r.  B. — It  is  well  known,  that  if  the  nerves  which 
are  distributed  to  a  muscle,  be  divided,  that  muscle  will 
be  found  to  be  entirely  beyond  our  control,  however  ea- 
ger our  wish,  or  strong  our  efforts  to  move  it. 

Emily.— 'It  appears  then,  that  when  a  nerve  is  divi- 
ded, it  is  neither  capable  of  transmitting  the  impressions 
made  on  its  extremities,  nor  of  conveying  the  stimulus 
of  volition  to  its  extremities.  Now  this  double  func- 
tion of  the  same  nerve  puzzles  me  exceedingly,  for 
functions  so  different,  one  would  imagine,  would  be  ex- 
ecuted by  different  instruments. 

Dr.  B. — This  reasoning  always  had  great  plausibility, 
and  its  truth  has  lately  been  most  satisfactorily  demonstra- 
ted by  Mr.  Charles  Bell.  He  was  first  led  to  correct 
views  of  this  subject,  by  thinking  on  the  difference  which 
the  nerves  of  the  spine,  and  the  brain,  present  in  regard 
to  their  origin,  or  as  we  have  called  it,  their  termination. 

The  former,  as  we  have  already  seen,  are  connected 
with  the  spinal  marrow  by  two  roots,  and  each  root  with 
a  distinct  track  or  column  of  nervous  matter,  three  of 
which  columns  compose  each  side  of  the  spinal  mar- 
row, and  may  be  easily  distinguished  through  its  whole 
Bourse,  and  even  in  the  brain  itself.  If  any  one  of  these 
nerves  be  divided,  both  the  sensation  and  the  motion  of 
the  part  to  which  it  leads,  are  lost.  The  nerves  of  the 
brain,  on  the  contrary,  are  connected  by  a  single  root 
only,  and  the  division  of  which,  is  found  to  occasion 
the  loss  of  but  one  of  these  powers.  Thus,  if  the  optic 
nerves  be  divided,  the  sense  of  vision  disappears,  but 
the  motions  of  the  eye  are  performed  as  readily  as  be- 
fore. To  ascertain  now,  whether  this  difference  of  pow- 
er depends  on  the  kind  of  connection  which  the  nerves 
maintain  with  the  brain  and  the  spinal  marrow,  he  de- 
termined to  divide  the  roots  of  the  spinal  nerves  singlv,, 
12* 


138  DISCOVERIES    OF    MR.    BELL. 

and  watch  the  effect.  The  spinal  canal  was  laid  open 
several  times  in  rabbits,  and  the  posterior  roots  of  the' 
nerves  of  the  lower  extremities  were  divided.  The  an- 
imal's motions  were  not  impeded,  but  the  extremity  was 
ascertained  to  be  utterly  destitute  of  sensation.  It  might 
be  pinched,  cut,  pricked,  or  otherwise  irritated,  without 
giving  the  creature  the  slightest  degree  of  pain.  In  the 
next  experiments,  the  anterior  roots  were  divided  and 
the  posterior  left  undisturbed.  The  limb  now  lost  all 
power  of  motion,  while  its  sensibility  remained  unimpair- 
ed. 

Emily. — The  spinal  nerves  are  in  reality,  then,  dou- 
ble nerves ;  but  do  they  continue  distinct  throughout 
their  whole  course,  even  to  their  extremities  ? 

Dr.  B. — They  continue  distinct,  but  we  are  not  able 
to  distinguish  them  on  account  of  their  very  intimate  con- 
nection. Each  nerve,  when  minutely  examined,  will  be 
found  to  be  an  aggregate  of  very  delicate  filaments,  bound 
up  in  a  common  cellular  envelope.  These  filaments  are 
for  the  purpose,  either  of  sensation,  or  motion,  and  they 
remain  distinct  from  one  another  in  their  whole  course, 
from  their  extremities  in  the  parts  which  they  supply 
with  nervous  power,  through  the  spinal  marrow,  to  their 
termination  in  the  brain. 

Emily. — And  this  too,  without  any  interference  with 
each  other  !  no  derangement  of  each  other's  functions  ! 
Truly  there  is  no  end  to  the  wonders  displayed  in  the 
construction  of  the  human  frame. 

Dr.  B. — Mr.  Bell  now  thought  that  this  view  of  the 
functions  of  the  nerves  would  be  confirmed,  if  after 
tracing  the  distinct  columns  of  nervous  matter  in  the 
spinal  marrow,  into  the  brain,  he  should  find  nerves  of 
motion  connected  with  the  anterior  column,  and  nerves 
of  sensation,  with  the  posterior  column.  This  fact  was 
also  satisfactorily  established.  Again,  he  saw  that  one 
nerve  of  the  brain,  the  fifth,  had  a  close  resemblance  to 
fhe  spinal  nerves,  being  connected  to  the  brain  by  two 
roots,  and  he  concluded  that  like  them,  it  was  a  nerve  of 


DISTINCTNESS    OP    THE    TWO    POWERS.  139 

sensation  and  motion.  This  opinion  was  tested  by  ex- 
periment. He  divided  it  in  an  ass,  and  the  jaw  to  which 
it  is  distributed,  instantly  fell  relaxed,  and  was  deprived  of 
all  sensibility. 

Emily. — I  should  think  his  opinions  were  established 
satisfactorily  enough  now.  But  what  other  functions 
does  the  nervous  power  possess  ?  I  think  you  mentioned 
that  these  which  we  have  already  considered,  are  not 
the  only  ones. 

Dr.  B. — It  is  known  to  possess  some  influence  in  the 
process  of  secretion,  for  if  the  nerve  be  divided  which  is 
distributed  to  a  secreting  organ,  the  secreting  process 
immediately  ceases.  How  this  influence  is  exerted,  we 
do  not  know.  It  is  also  inferred  with  a  great  deal  of 
reason,  that  the  nervous  power  takes  no  small  part  in  the 
production  of  animal  heat. 

Such  are  the  functions  of  the  nervous  power  ;  and  that 
this  power  is  perfectly  different  from  the  sensorial,  is  ca- 
pable of  unexceptionable  proof. 

Emily. — I  am  glad  you  have  mentioned  this,  for  I  was 
just  about  to  ask  you  for  more  definite  evidence  of  their 
distinctness.  We  cannot  distinguish  between  the  im- 
pression and  the  sensation — they  seem  to  be  one  and  the 
same  act,  and  I  confess,  I  see  no  evidence  why  they  are 
not  both  the  result  of  one  general  power. 

-D**-  B  — We  know  that  they  are  distinct,  because  one 
may  continue  in  action  while  the  other  is  destroyed,  or 
prevented  from  action.  Thus,  in  some  diseases  or  inju- 
ries of  the  brain,  volition,  sensation,  consciousness  may 
be  entirely  lost,  and  yet  the  process  of  secretion  and  the 
evolution  of  animal  heat  be  still  continued  for  a  consider- 
able time. 

Emily. — Hence  it  seems  that  impressions  made  on  the 
nerves,  are  not  transmitted  to  the  brain,  and  this  you 
considered  an  important  duty  of  the  nervous  power. 

Dr.  B. — We  have  jno  right  to  say  that  the  nerves  do 
not,  in  such  cases,  transmit  the  impressions  which  they 
receive,  because  if  we  irritate  them,  we  see  that  the  rnus- 


140  THEORIES    0F    THE    NERVOUS    POWER. 

cles  to  which  they  are  distributed,  are  violently  convul- 
sed. The  fact  is,  that  though  the  impressions  are  trans- 
mitted to  the  brain,  the  sensorial  power  being  destroyed 
or  suspended,  does  not  furnish  the  stimulus  of  volition, 
nor  produce  sensation.  In  sleep  we  see  some  of  the 
nervous  functions  suspended ;  while  the  sensorial  are 
in  full  play  &nd  activity.  We  think,  feel  and  will,  but 
not  a  muscle  obeys  the  stimulus  of  volition,  because  the 
nervous  power  does  not  transmit  it. 

Emily. — I  am  satisfied  now,  perfectly.  But  it  ap- 
pears to  me,  you  have  neglected  to  say  any  thing  of  the 
manner  in  which  impressions  and  volitions  are  commu- 
nicated by  the  nerves,  or  in  other  words  perhaps,  the  na- 
ture of  the  nervous  power.  This  seems  to  me  to  be  the 
most  interesting  part  of  the  subject. 

Dr.  B. — And  it  is  as  obscure,  as  it  is  wonderful  and 
curious.  Still,  little  as  we  actually  know  about  itj  there 
has  been  no  lack  of  theories  to  explain  its  nature,  and 
shed  broad  daylight  upon  the  dark  obscurity.  By  one 
of  these  theories,  it  was  supposed  that  the  nerves  had  the 
power  of  vibration,  anH  the  word  nerve  itself,  which 
means  a  tense  cord,  shows  how  common  this  opinion 
was  among  the  Greeks.  This  theory,  which  for  a  long 
time  had  fallen  into  disrepute,  was  revived  during  the 
last  century,  with  modifications  and  improvements,  by 
Dr.  Hartley.  It  is  unaccountable  how  such  a  theory 
should  have  ever  prevailed,  for  we  can  conceive  of  no 
part  of  the  animal  structure  so  entirely  incapable  of  the 
vibratory  motions  of  a  tense  string,  as  the  delicate,  inelas- 
tic nerves  completely  enveloped  in  the  surrounding  soft 
parts.  By  another  theory,  the  nerves  were  regarded  as 
capillary  tubes  which  convey  a  fluid  secreted  by  the 
brain,  and  called  the  nervous  fluid  or  animal  spirits.  It  is 
by  the  oscillations  of  this  fluid,  that  impressions  are  com- 
municated to  the  brain,  and  volitions  to  the  nerves.  It 
has  been  a  very  common  doctrine  among  medical  men, 
and  seems  now  to  be  an  article  of  popular  belief.  It  is 
enough  to  say  of  it  however,-  that  the  two  essential  facts 


"DR.    PHILIP'S    EXPERIMENTS.  141 

upon  which  the  whole  theory  depends  have  been  gratu- 
itously assumed, — the  nerves  have  never  been  found  to 
be  hollow,  and  the  nervous  fluid,  such  as  it  is  here  im- 
agined, never  existed. 

Emily. — Is  it  possible  that  with  no  foundation  what- 
ever in  truth,  this  theory  could  have  prevailed  so  long  ! 

Dr.  B. — It  seemed  reasonable  enough  that  the  com 
raunication  maintained  by  the  nerves,  should  be  effected 
by  means  of  some  material  agent,  for  it  was  hardly  pos- 
sible to  conceive  how  else  it  could  be  done.  In  accord- 
ance with  the  most  common  analogies,  it  was  very  nat- 
urally regarded  as  an  extremely  light  fluid,  or  invisible 
gas.  In^later  times,  the  nature  of  that  subtle  and  pow- 
erful agent,  electricity,  has  been  more  fully  unfolded  to 
us,  and  now,  the  most  common  theory  of  the  nervous 
power  identifies  it  with  this  agent.  The  modern  discov- 
eries in  regard  to  it,  very  soon  showed  its  strong  resem- 
blance to  some  of  the  vital  actions,  and  great  expecta- 
tions' were  raised,  that  it  would  be  found  one  day,  to 
constitute  an  important  property,  or  portion  of  organized, 
matter. 

Emily. — Galvani,  I  believe,  ascertained  that  if  a  frog 
formed  part  of  a  galvanic  circle,  violent  and  rapid  con- 
tractions of  the  muscles  took  place. 

Dr.  B. — It  is  well  known  too,  that  the  dead  body, 
when  properly  exposed  to  its  influence,  will  exhibit  some 
of  the  most  striking  phenomena  of  life.  The  chest  has 
been  made  to  contract  and  dilate,  as  in  true  respiration  ; 
the  fist  has  been  clenched  ;  the  limbs  raised ;  and  the 
passions  strongly  expressed  in  the  countenance.  The 
brilliant  experiments  of  Dr.  Wilson  Philip  have  partic- 
ularly called  attention  to  this  fluid,  and  convinced  many 
of  its  perfect  identity  with  the  nervous  power.  It  is  well 
known,  that  if  the  nerves  which  are  distributed  to  the 
organs  of  respiration  and  digestion,  are  divided,  the  for- 
mer function  is  impeded,  and  soon  ceases,  and  the  latter 
is  effectually  destroyed.  Now  this  gentleman  divided 
these  nerves  in  different  animals,  and  connected  their 


142   GALVANISM  AND  THE  NERVOUS  POWER. 

divided  extremities  with  a  galvanic  battery  by  which  they 
were  supplied  with  a  regular  current  of  the  galvanic 
fluid.  The  result  of  these  experiments  was,  that  these 
functions  might  be  maintained  in  this  manner  perfectly 
well  for  a  considerable  length  of  time.  For  instance, 
the  nerves  were  divided  in  two  small  dogs,  soon  after 
they  had  been  permitted  to  eat  as  much  mutton  as  they 
chose.  In  one  of  them,  galvanism  was  applied  for  two 
hours  and  a  quarter,  when  he  died.  On  examination, 
the  food  was  found  half  digested.  The  other  dog  which 
was  not  galvanized,  died  at  the  end  of  four  hours,  when 
it  was  found  that  the  food  he  had  eaten,  was  not  in  the 
slightest  degree  digested,  but  retained  perfectly  the  ap- 
pearance it  had  when  it  was  swallowed. 

Emily. — Well,  really,  if  there  has  been  no  fallacy  in 
these  experiments,  how  can  we  resist  the  conclusion,  that 
the  galvanic  and  nervous  powers  are  but  one  and  the 
same  power  ?  I  am  sure  it  seems  impossible  to  me. 

Dr.  B. — To  this  opinion  it  is  replied,  that  these  ex- 
periments prove  merely  an  analogy  between  the  galvan- 
ic and  nervous  powers, — that  they  possess  some  com- 
mon properties  by  virtue  of  which  the  former  may  be 
substituted  a  short  time  for  the  latter, — that  their  identity 
is  no  more  proved  by  their  similar  effects  on  the  vital 
actions,  than  the  violent  contractions  produced  in  a  mus- 
cle by  pricking  it  with  a  pin,  or  irritating  it  with  chemi- 
cal and  mechanical  agents,  indicate  the  nervous  power 
to  be  identical  with  any  of  these  agents. 

Emily. — This  reasoning  however,  does  not  satisfy 
me.  The  sole  object  of  the  nervous  power  is  to  assist 
in  the  vital  actions,  and  if  the  galvanic  fluid  be  found 
to  answer  the  same  purpose,  at  least  as  far  as  can  be  ex- 
pected considering  how  it  is  applied,  why,  it  seems  to 
jme  almost  conclusive  proof  of  their  identity. 

Dr.  B. — Think  which  way  you  will  on  the  subject, 
you  will  have  the  satisfaction  of  knowing  that  many  emi- 
nent physiologists  are  on  your  side.  But  to  confirm  your 
opinion,  behold  the  following  among  several  marvellous 


THE  SENSORTAL  POWER.  143 

experiments  lately  performed  by  Weinhold.  He  remo- 
ved the  brain  and  spinal  marrow  of  a  cat,  and  after  all 
signs  of  life  had  disappeared,  he  filled  up  the  cranium 
and  vertebral  canal  with  an  amalgam  of  mercury,  zinc, 
and  silver.  The  effect  was,  that  the  animal  soon  gave 
signs  of  life  ;  it  raised  its  head,  opened  its  eyes,  looked 
steadily,  attempted  to  walk,  and  endeavoured  to  rise  af- 
ter frequently  tailing  down.  In  the  mean  time,  the  cir- 
culation was  renewed,  and  the  secretion  of  the  gastric 
juice  seemed  more  abundant  than  ordinary.  The  ani- 
mal heat  was  also  re-established.  This  gentleman  also 
remarked,  that  the  extremities  of  a  divided  nerve  gave 
sparks  when  brought  together. 

Emily. — A  most  marvellous  experiment  truly,  and  not 
without  its  practical  utility  too,  for  perhaps  in  time,  some 
more  perfect  composition  may  be  found  which  will  re- 
store even  the  creature's  mousing  propensities,  and  in 
short,  make  it  once  more,  sound  and  healthy  as  ever. 

Dr.  B. — We  must  now  turn  our  attention  to  the  sen- 
sorial  power.  In  regard  to  sensation,  we  know  no  more 
than  that  a  certain  series  of  changes  invariably  precede 
its  appearance,  and  that  its  seat  is  somewhere  in  the  brain. 
We  can  define  it  only  by  mentioning  these  changes  which 
has  been  already  done.  In  the  first  place  an  impression 
is  made  from  the  external  world,  upon  an  organ  ex- 
pressly destined  to  receive,  ,and  prooerly  modify  it. 
By  means  of  a  nevre  in  connection  with  this  organ,  the 
impression  is  communicated  to  the  brain.  Lastly,  it  is 
received  into  the  brain,  and  recognized  by  the  mind. 

Emily. — Is  it  necessary,  Dr.  B.,  that  each  of  these, 
stages  must  be  passed  through,  in  order  that  sensation 
rnay  take  place  ?  What  would  be  the  effect  of  irritating 
the  nerve  of  vision,  for  instance  ? 

Dr.  B. — The  effect  would  be  that  neither  motion 
nor  sensation  would  be  produced.  If  the  organ,  nerve 
or  part  of  the  brain  whither  the  impression  is  carried,  be 
destroyed  or  injured,  no  sensation  will  be  produced. 


144  PHRENOLOGY. 

Emily. — In  what  part  of  the  brain  does  this  faculty 
of  sensation  reside  ? 

Dr.  B. — This  is  a  question  not  so  easily  answered  as 
might  at  first  sight,  be  supposed  ;  for  though  the  brain 
has  been  examined  with  more  care,  interest,  and  perse- 
verance than  any  other  organ  in  the  body,  yet  very  little 
is  certainly  known  of  the  functions  of  its  various  parts. 
The  older  physiologists  thought  there  must  be  some  com- 
mon point  in  the  brain  where  all  the  nerves  terminated, 
and  whither  all  the  impressions  are  conveyed.  This 
spot  they  were  accustomed  to  call  the  sensorium  com- 
mune, or  common  sensorium,  -and  it  was  located  in  vari- 
ous parts  of  the  brain,  according  as  whim,  or  hypothesis 
dictated.  As  for  the  source  of  volition,  we  know  no 
rnore  than  about  that  of  sensation.  Many  experiments 
lave  been  performed  with  the  view  of  throwing  light  on 
;his  subject,  but  at  present  their  results  are  too  clashing 
to  warrant  us  in  deducing  from  them,  any  general  truths. 
As  for  the  intellectual  faculties,  modern  physiologists  have 
been  fond  of  assigning  them  distinct  seats  in  the  brain, 
and  lately  this  view  of  the  matter  has  been  extensively 
developed  and  wrought  up  into  a  regular  system  which 
is  exceedingly  plausible  and  has  been  received  by  many — 
and  some  very  distinguished — physiologists. 

Emily. — O,  you  allude  to  Phrenology.  Do  tell  me 
something  about  this  system,  for  the  accounts  respecting 
it  are  so  contradictory  that  one  can  hardly  tell  from 
them,  whether  to  consider  it  as  the  dreams  of  visiona- 
ries, or  the  results  of  sound  philosophy. 

J)r,  J5. — Such  is  always  the  case,  when  men  under- 
take the  discussion  of  doctrines,  with  minds  already  oc- 
cupied by  violent  prejudices.  But  you  may  be  assured, 
that  a  science,  which  within  thirty  years  has  been  gain- 
ing ground  so  fast,  that  it  now  numbers  among  its  advo- 
cates some  of  the  most  distinguished  scientific  men  of 
the  present  day  ;  that  pretends  to  establish  its  principles 
only  on  numerous  and  well  observed  facts,  cannot,  with 
the  slightest  justice,  be  associated  with  the  fancies  of 


PHRENOLOGY.  145 

dreamers,  or  fanatics,  but  is  worthy  the  examination  of 
all  sound  and  inquiring  minds.  According  to  phrenolo- 
gy, the  brain  is  an  aggregate  of  several  organs  of  a  con- 
ical form,  originating  by  their  apex  from  a  common 
point  in  the  centre  of  the  brain,  and  terminating  by  their 
base  on  its  circumference.  These  organs  are  the  seat 
of  the  various  moral  and  intellectual  faculties,  which  are 
distinct  from,  and  in  some  measure  independent  of  each 
other.  Those  to  which  the  intellectual  faculties  belong, 
occupy  the  front  part  of  the  head,  while  the  moral  and 
animal  passions  are  exercised  by  the  middle  and  poster- 
ior portions.  The  strength  or  capacity  of  the  faculties, 
is  in  a  direct  proportion  to  the  size  of  these  particular 
organs,  and  that  of  the  whole  brain.  The  relative  size 
of  any  particular  organ,  and  the  strength  of  its  correspond- 
ing faculty  may  be  estimated  by  examining  itst  ermina- 
tion  on  the  surface  of  the  brain.  If  it  swells  above  the 
rest,  appearing  like  a  bump  or  protuberance,  the  organ  is 
large  and  well  developed,  and  the  faculty  will  form  a 
prominent  feature  in  his  moral,  or  intellectual  character. 

Emily. — But  Dr.  B,,  when  you  described  the  brain, 
you  said  nothing  of  these  organs  which  are  the  very 
foundation  of  the  phrenological  doctrine. 

Dr.  B. — They  were  not  mentioned,  because  in  truth 
they  cannot  be  distinguished.  All  the  other  proposi- 
tions of  phrenology  may  be  established  by  fact,  or  sound 
reasoning,  but  as  to  the  form,  size,  or  even  existence 
of  these  organs,  anatomy  gives  us  no  light  whatever. 

Emily. — May  not  the  strength  of  any  particular  fac- 
ulty depend  in  some  degree  on  the  fineness  and  perfec- 
tion of  structure,  as  well  as  absolute  size  of  the  organ. 
It  is  not  those  who  have  the  largest  eyes  or  ears  that  see 
or  hear  best,  or  those  who  have  the  largest  muscles  that 
can  lift  most,  and  why  should  he  who  has  the  largest 
organs,  or  brains,  think  and  feel  most  strongly  ? 

Dr.  B. — Perhaps  the  perfection  of  a  faculty  depends 
in  some  degree  on  organization,  but  there  are  strong 
grounds  for  believing  that  it. depends  chiefly  on  size. 
13 


146  PHRENOLOGY. 

Emily. — If  that  were  true  then,  we  should  always  ex- " 
pect  that  persons  possessing  large  heads,  would  be  like- 
wise men   of  great  intellectual  powers,  and  vice  versa. 
But  is  this  the  case  ?     Is  not  the  capacity  of  the  mind 
entirely  independent  of  the  size  of  head  ? 

Dr.  B. — Not  according  to  the  testimony  of  the  best 
observers.  Those  who  have  given  this  subject  particu- 
lar attention,  are  agreed  in  considering  that  great  men- 
tal capacity  is  accompanied  by  a  large  head.  Hear 
what  Majendie  says — one  of  the  most  distinguished 
physiologists  of  the  age;  distinguished  not  more  for  the 
brilliancy  of  his  discoveries,  than  the  philosophical  spirit, 
that  pervades  all  his  researches.  "  Generally  speaking, 
the  volume  of  the  brain  is  in  direct  proportion  to  the  ca^ 
pacity  of  the  rnind.  It  would  be  incorrect  however,  to 
suppose  that  every  man  who  has  a  large  head,  must  ne- 
cessarily be  possessed  of  a  superior  intellect,  because  ma- 
ny causes  besides  the  volume  of  the  brain,  may  increase 
the  size  of  the  head.  But  it  is  nevertheless  very  rare 
that  a  man  distinguished  for  his  mental  faculties,  is  not 
found  to  have  a  large  head."  That  the  strength,  and 
even  the  kind  of  intellectual  power  is  indicated  in  a  great 
degree  by  the  size  and  form  of  the  head,  is  a  doctrine  of 
no  recent  date,  but  was  most  distinctly  recognized  by  the 
ancient  artists.  The  old  sculptors  never  committed  the 
solecism  of  putting  the  head  of  a  philosopher  on  the 
shoulders  of  a  gladiator  ;  and  the  character  of  their 
Deities,  of  Jove  the  Thunderer,  of  Apollo  the  patron  of 
the  muses  and  the  arts,  of  Mars  the  God  of  brute  force, 
is  strikingly  indicated  by  the  form  of  the  head,  no  less 
than  by  the  features  of  the  face.  In  the  paintings  of  the 
modern  masters,  the  same  principle  has  been  steadily 
kept  in  view,  though  the  doctrines  of  phrenology  never 
came  to  their  ears.  It  is  every  day  recognized  to  a  cer- 
tain extent,  by  the  most  ordinary  observers,  for  he  who 
should  be  liable  to  mistake  the  head  of  an  idiot,  for 
that  of  Bacon  or  Shakespeare,  would  be  considered  al- 
most an  idiot  himself. 


PROPORTION    OF  THE    BRAIN    TO    THE  BODY.       147 

Emily. — As  man  has  greater  intellectual  faculties  than 
any  other.animal,  then,  according  to  this  doctrine,  he  must 
have  the  greatest  head,  in  proportion  to  his  body,  of  all 
other  animals. 

Dr.  B. — This  does  not  necessarily  follow,  because 
the  whole  brain  is  not  supposed  to  be  devoted  to  the  ex- 
ercise of  the  intellectual  faculties.  Still  it  is  so  general- 
ly true,  that,  at  one  time  it  was  a  commonly  received 
opinion,  though  many  exceptions  now  brought  to  light, 
destroy  its  force  as  a  universal  rule. 

Emily. — Do  mention  some  of  these  exceptions ;  I  am 
curious  to  know  what  animals  have  a  larger  brain  than 
the  "  lord  of  creation." 

Dr.  B. — It  has  been  ascertained  that  the  dolphin, 
some  of  the  seals,  several  apes,  and  some  birds,  exceed 
the  human  species  in  this  particular ;  and  an  exami- 
nation of  the  proportions  of  many  other  inferior  ani- 
mals, shows  that  the  intellectual  capacity  is  not  always 
proportional  to  the  relative  size  of  the  brain.  Thus,  in 
man,  the  brain  bears  to  the  body,  the  proportion  of  1  to 
22,  33,  and  sometimes  35  ;  in  the  dog,  it  is  as  1  to  100  ; 
in  the  elephant,  as  1  to  500  ;  in  the  sheep,  as  1  to  257 ; 
in  the  horse,  as  1  to  700  ;  in  the  ass,  as  1  to  154;  in 
the  eagle,  as  1  to  260  ;  in  the  duck  as  1  to  257  ;  in  the 
tortoise,  as  1  to  2240  ;  in  the  frog,  as  1  to  172  ;  in  the 
shark,  as  1  to  2496 ;  in  the  carp,  as  1  to  580. 

Emily. — Truly,  we  may  bid  good  bye  to  theory  now. 
Here  is  the  ass,  the  very  emblem  of  stupidity,  with  four 
times  more  brain  than  his  nobler  brother,  the  horse;  and 
the  elephant,  the  most  sagacious  among  brutes,  exceeded 
in  point  of  brain,  by  the  silly  sheep.  But  what  are  the 
proportions  in  those  animals  which  you  mentioned  as 
being  exceptions  to  the  principle  that  man  possesses  the 
largest  brain  in  proportion  to  his  body  ? 

Dr.  B. — In  the  dolphin,  the  brain  is  to  the  body,  as 
1  to  25  ;  in  the  Canary  bird,  as  1  to  14  ;  in  the  sparrow, 
as  1  to  25  ;  in  the  red  breast,  a  1  to  32.  Thus,  you 
see  most  strikingly,  how  such  facts  are  worth  volumes 
of  speculation. 


H8  FACIAL    ANGLE. 

Emily. — But  may  not  the  human  brain  after  all,  be 
absolutely  larger  than  that  of  any  other  animal  ? 

Dr.  B. — Such  was  the  belief  of  the  ancient  natural- 
ists, and  it  is  certainly  less  objectionable  on  the  score  of 
exceptions,  than  the  other,  for  the  elephant  is  the  only 
one  I  believe  that  has  been  found. 

Another  point  of  comparison  has  been  instituted,  which 
is  more  satisfactory  than  either  of  these.  It  depends  on 
the  ratio  of  the  brain  to  tile  bulk  of  the  nerves  which  is- 
sue from  it.  This  view  of  the  matter  flatters  our  pride 
more  than  any  other,  for  man  possesses  positively  the 
largest  brain  in  proportion  to  the  nerves  which  come  out 
from  it.  The  apes,  whose  brain  resembles  man's  so 
much  in  form  and  size,  present  a  striking  difference  in 
the  size  of  their  nerves.  The  brain  of  the  horse  is  14 
ounces  lighter  than  man's,  while  the  nerves  in  its  base 
are  ten  times  larger. 

Emily. — Is  there  no  other  difference .  between  the 
brain  of  man  and  of  the  mammiferous  animals,  than  that 
of  size  and  form  ?  I  should  imagine  there  might  be  some 
difference  in  the  organization,  the  one  being  more  deli- 
cate and  perfect  in  this  respect. 

Dr.  B. — They  all,  except  the  apes,  want  the  poste- 
rior portions  of  the  cerebrum.  In  man,  all  the  parts  are 
more  developed,  the  convolutions  are  deeper  and  more 
numerous,  and  it  approaches  nearest  the  spherical  shape. 
But  the  most  striking  characteristic  of  the  human  brain, 
is  the  prodigious  developement  of  the  cerebrum,  and 
especially  its  anterior  portion.  The  proportion  between 
this  part,  as  it  is  considered  to  be  most  closely  connect- 
ed with  the  mental  powers,  and  the  rest  of  the  brain,  is 
a  tolerable  index  of  the  mental  capacity  of  the  animal. 

Emily. — But  how  can  we  ascertain  this,  till  after  the 
animal  is  dead  ?  I  do  not  see  how  the  fact  can  be  of 
any  practical  utility,  unless  we  have  the  means  of  deter- 
mining it  during  life. 

Dr.  B. — Several  rules  for  this  purpose  have  been 
laid  down  by  naturalists,  but  we  can  mention  only  that 


FACIAL    ANGLE, 


149 


of  Camper,  called  the  facial  angle.  He  imagines  a 
straight  line  drawn  from  the  forehead  to  the  upper  lip, 
and  another  forming  an  angle  with  it,  from  the  lip  hori- 
zontally backwards.  As  the  prominence  of  the  fore- 
head is  produced  by  the  cerebrum,  the  greater  the  lat- 
ter is,  the  greater  will  this  angle  be.  In  a  well-formed 
European  head,  the  facial  angle  is  about  85°,  as  is  rep- 
resented in  this  figure  ;  in  some  of  the  Grecian  statues 


of  the  gods,  it  is  frequently  over  90,°  thus  indicating  the 
supernatural  perfection  of  the  Deity. 

Emily. — The  poor  Negro  must  suffer  sadly  by  this 
test,  for  not  only  is  his  forehead  low  and  retreating,  but 
his  jaws  project  considerably — at  least  the  upper  one 
does — a  circumstance  which  will  materially  lessen  the 


angle. 


o — 

Dr.  B. — True  it  is  rather  an  unfair  test,  when  appli- 
ed  to  the   Negro,   in  whom  the  angle  is  7°  or  8Q  less 
than  in  the  European,  as  you  may  see  by  comparing  this 
next   figure,   which  represents  the  Nescro's  skull,  with 
13* 


POSITON    OF    THE    FACli. 
tf 


the  first.  In  all  children  the  angle  is  much  larger  than 
in  adults,  for  at  their  time  of  life,  the  cerebrurif  is  more 
fully  developed. 

Emily. — How  do  the  lower  animals  appear  when  tri- 
ed by  this  test  ? 

Dr.  B. — In  the  larger  monkies,  it  varies  in  differ- 
ent species  from  70°to  80°, 
as  represented  in  this  figure. 
In  the  sheep  and  hog,  we 
find  it  not  more  than  35Q. 
In  the  birds,  the  angle  suf- 
fers a  very  considerable  di- 
minution not exceeding  gen- 
erally 7°  or  8Q.  In  the  rep- 
tiles, it  is  still  less,  and  in  the 
fishes  it  is  almost  nothing. 
It  may  be  remarked  generally,  that  in  the  European 
the  face  is  placed  nearly  perpendicularly  under  the 
front  of  the  cranium  ;  in  the  Negro,  and  some  other 
varieties  of  the  race,  we  see  it  beginning  to  be  placed 
more  in  front,  projecting  forward  ;  and  in  the  lower  ani- 
mals, forming  a  great  part  of  the  head.  As  we  descend 
^he  animal  scale,  this  increasing  size  of  the  face,  inclu- 
Hng  also  that  of  the  jaws,  indicates  very  strongly  the  in- 


REASON.  151 

creasing  predominance  of  the  animal  over  the  moral  and 
intellectual  nature.  If  therefore  we  consider  the  brain 
as  the  exclusive  organ  of  the  moral  and  intellectual  fa- 
culties, and  the  rest  of  the  nervous  system,  as  that  of  the 
senses  merely,  then  certainly  the  comparison  of  the 
cranium  and  face,  must  throw  considerable  light  on  the 
dispositions  and  capacities  of  animals. 

Emily. — What  would  be  the  result  of  such  a  compa- 
rison in  man  ? 

Dr.  B. — Man  has  the  largest  cranium  with  the 
smallest  face,  and  his  intellectual,  compared  with  his  ani- 
mal faculties,  are  greatly  superior  to  those  of  any  other 
animal. 

Reason,  or  intelligence,  whatever  we  choose  to  call  it, 
is  not  peculiar  to  man,  but  exists  in  the  brutes  in  various 
degrees  of  perfection. 

Emily. — Brutes  have  instinct,  it  is  true,  but  I 
thought  this  was  very  different  indeed  from  reason. 

Dr.  B. — It  is  ;  but  the  brutes,  as  well  as  man,  have 
a  certain  degree  of  each.  Instinct  impels  them  to  the 
performance  of  certain  actions  necessary  to  fulfil  the 
purposes  of  their  nature,  without  premeditation  or  design. 
Thus,  when  the  young  pup  is  thrown  for  the  first  time 
into  the  water,  or  the  new-born  babe  placed  at  the  ma- 
ternal breast,  it  is  instinct  which  impels  each  to  a  most 
complicated  series  of  muscular  motions  but  which  are  ne- 
cessary for  the  preservation  of  life.  But  reason,  consider- 
ed as  the  power  of  "  shaping  means  to  ends,"  though 
possessed  in  some  degree  by  the  brutes,  exists  in  man 
in  its  highest  state.  Its  ceaseless  action  is  carrying  on 
the  species  in  its  unlimited  progress,  and  indissolubly 
associating  the  happiness  of  the  individual,  with  that  of 
the  whole  community. 

Emily. — And  in  the  brutes  too,  the  deductions  of 
reason,  as  you  are  pleased  to  call  it,  are  confined  to  the 
individual — he  alone  enjoys  their  benefits.  But  in  man, 
they  constitute  a  common  stock,  to  which  all  contribute, 
and  from  which,  all  receive  a  share. 


162  REASON; 

Dr.  B. — What  he  wants  in  physical  power  to  consti- 
tute him  "  lord  of  the  creation,"  is  amply  made  up  by 
this  instrument,  by  means  of  which  the  inferior  animals 
are  deprived  of  their  natural  independence,  and  made 
subservient  to  his  changing  wishes.  The  brute  is  not 
taught  by  it  the  offices  of  kindness,  nor  impressed  with 
a  single  desire  to  advance  the  welfare  of  his  species. — 
Man  alone  "  feels  for  man,"  relieves  his  distresses,  and 
rejoices  in  his  prosperity.  Give  to  the  reason  of  the  in- 
ferior animals  as  high  a  character  as  you  please,  it  still 
remains  the  highest  and  noblest  prerogative  of  man  ; 
the  faculty  that  removes  him  to  an  immeasurable  dis- 
tance from  every  other  being  in  the  wide  creation,  and 
points  him  to  the  Divinity  for  fellowship. 


CONVERSATION  VII. 


The   senses — the    eye — eye-brows — eye-lids — eye-lashes 

— tears — sclerotic  coat choroid — cornea iris — 

aqueous  humor — crystalline  lens — retina — modifica- 
tion of  the  rays  by  the  coats  and  humors — short-sight- 
edness— motions  of  the.  eyes — squinting — vision  as- 
sisted by  the  other  senses. —  Vision  of  birds — of  fishes — 
of  insects. — Hearing — sound — anatomy  of  the  ear — 
hearing  assisted  by  the  other  senses — hearing  of  the 
inferior  animals. — Smelling — use  of  the  sense  of  smell 
— smelling  of  the  inferior  animals. — Taste — influence 
of  civilization  upon  taste — taste  of  the  inferior  ani- 
mals— the  touch — integuments — human  complexion — 
albinos. — The  voice — larynx — larynx  of  the  inferior 

animals — cries — language — singing ventriloquism 

— voice  of  birds. 

Dr.  B. — By  the  organs  of  the  senses,  we  refer  to 
those  by  means  of  which,  impressions  made  on  certain 
portions  of  the  nervous  system,  are  conveyed  to  the 
brain,  and  there  excite  corresponding  sensations.  The 
senses  may  be  said  to  be  the  bond  of  connection  in  the 
animal  between  the  external  and  internal  world  ;  and 
raising  the  creature  above  the  state  of  mere  vegetable 
existence,  they  place  him  in  close  relations  with  the  ob- 
jects around  him,  arid  give  him  an  elevated  rank  in  the 
general  system  of  nature.  Each  one  gives  him  an  en- 
tirely distinct  set  of  ideas,  which  he  could  have  obtained 


154  EYEBROWS. 

in  no  other  way.  Deprive  him  of  the  eye,  and  where 
is  the  beauty  of  colours  ?  Of  the  ear,  and  where  is  the 
melody  of  sounds  ?  Of  the  nose,  and  where  is  the  fresh- 
ness and  fragrance  of  smells  ?  Take  away  from  him  all, 
and  he  is  reduced  to  a  mere  vegetable  existence. 

Emily. — Can  we  not  then  easily  conceive,  how  an  ad- 
ditional sense,  by  making  us  acquainted  with  the  quali- 
ties of  objects  of  which  we  are  now  altogether  ignorant, 
would  give  us  another  set  of  ideas,  and  thus  enlarge  and 
elevate  our  capacities  ? 

Dr.  B. — Why  in  truth,  there  is  nothing  very  chi- 
merical in  the  idea,  for  in  ascending  the  scale  of  animals, 
we  observe  the  senses  gradually  increasing  in  number 
and  perfection,  and  it  is  a  very  reasonable  supposition, 
that  five  may  not  be  the  utmost  limit  beyond  which  the 
possibility  of  any  more  is  precluded.  We  cannot,  how- 
ever, wish  for  any  more,  for  our  place  in  the  system  of 
nature  is  fixed,  and  our  capacities  are  sufficient  for  the 
conditions  of  our  exis  tence.  But  we  must  leave  these 
speculations,  and  proceed  to  our  account  of  the  senses ; 
anchfirst  let  us  consider  the  sense  of  sight. 

Emily. — Don't  be  afraid,  Dr.  B.,  of  being  too  par- 
ticular in  describing  the  various  parts  of  the  eye,  and 
the  uses  of  each,  for  I  am  exceedingly  desirous  of  fully 
understanding  the  construction  of  this  curious  organ. 

Dr.  B. — Before  we  consider  the  proper  organ  of 
vision,  we  must  give  a  passing  notice  of  its  protecting 
parts.  The  eye-brows  are  peculiar  to  man,  and  when 
contracted,  as  in  frowning,  they  serve  to  protect  it  from 
the  too  strong  impression  of  light,  and  prevent  the  sweat, 
particles  of  dust,  &tc.,  from  falling  into  the  eye.  The 
eye-lids  protect  it  from  the  immediate  contact  of  external 
objects,  and  this  end  is  still  farther  promoted  by  their 
peculiar  sensibility,  which  excites  them  to  close  over  the 
eye  instinctively,  on  the  approach  of  danger.  They 
likewise  regulate  in  a  certain  degree,  the  quantity  of  light 
which  enters  the  eye  ;  for  when  the  light  is  weak,  or 
fte  object  at  considerable  distance,  they  open  widely  -3 


TEARS.  155 

but  when  it  is  too  vivid,  they  approach  each  other,  and 
diminish,  as  far  as  necessary,  the  quantity  of  light. 

Emily. — But  what,  pray,  can  be  the  use  of  the  eye- 
lashes ?  Or  are  they  merely  for  ornament's  sake  ;  for 
you  know,  they  sometimes  look  very  beautiful,  and 
moreover,  furnish  a  poet  a  capital  subject  for  a  sonnet. 

Dr.  j^.-^I  apprehend  they  were  neither  designed  to 
add  beauty  to  the  human  face,  nor  to  inspire  a  poet's 
muse,  but  for  purposes  of  real  utility.  Their  use  is  sim- 
ilar to  that  of  the  eye-brow,  for  they  guard  the  eye  from 
insects  and  light  substances  floating  in  the  air  ;  and  so 
necessary  are  they  in  this  respect,  that  persons  who 
have  lost  their  eye-lashes,  are  always  troubled  more  or 
less  with  a  defect  of  vision. — For  furnishing  the  requi- 
site moisture,  by  which  the  parts  are  enabled  to  glide 
over  each  other  without  experiencing  any  ill  effects 
from  friction,  the  eye-lids  are  provided  with  numerous 
little  glands,  from  which  a  watery  fluid  is  secreted.  Be- 
sides this,  there  is  another  fluid,  the  tears,  secreted  from 
the  lacrymal  gland  situated  at  the  anterior  and  outer 
part  of  the  orbit,  (the  name  of  the  bony  socket  that  con- 
tains the  eye.)  When  any  thing;irritates  the  eye,  the 
tears  are  shed  in  prolusion,  for  the  purpose  of  washing 
away  the  irritating  cause. 

Emily. — What  becomes  of  the  tears  when  not  wanted 
for  this  purpose  ?  I  suppose  nevertheless,  that  their  se- 
cretion is  continually  going  on. 

Dr.  B. — This  is  readily  explained.  At  the  internal 
angle  of  the  eye,  there  are  several  minute  orifices  lead- 
ing by  a  short  canal  into  the  nose,  by  which  the  tears 
are  conducted  off,  and  thus  prevented  from  coming  out 
arid  falling  over  the  cheek — a  circumstance  which  would 
happen  if  these  orifices  were  closed,  as  they  sometimes 
are  in  disease. 

Emily. — And  the  reason  why  they  run  over  the 
cheek  in  crying,  is,  I  suppose,  because  they  are  poured 
forth  in  too  large  quantity,  to  be  absorbed  instantly  by 
these  lacrymal  orifices. 


156  COATS    OF    THE    EYE. 

Dr.  B. — Yes,  just  so.  The  organ  of  vision,  and  the 
mechanism  by  which  the  rays  of  light  are  transmitted 
through  it  and  variously  modified,  you  must  bear  in 
mind,  are  regulated  strictly  upon  optical  principles.  The 
whole  globe  ol  the  eye  is  a  collection  of  humors,  or  thick 
dense  fluids  arrayed  in  a  certain  order,  separated  from 
one  another,  and  enclosed  by  several  membranes  of  dif- 
ferent density  and  extent,  called  its  coats.  These  may 
be  arranged  in  three  divisions  ;  the  first,  serving  to  mod- 
ify the  rays  of  light  ;  the  second,  to  receive  the  im- 
pressions ;  and  the  third,  to  transmit  them  to  the  brain. 
And  now  for  those  of  the  first  division.  The  external 
and  enveloping  coat  of  the  eye  is  the  sclerotic,  a  strong 
fibrous  membrane,  nearly  of  a  spherical  shape,  which 
contains  and  protects  the  contents  of  the  eye,  and  pre- 
serves its  general  shape.  Lining  this,  is  the  choroid 
coat,  of  a  more  delicate  structure,  abundantly  provided 
with  blood-vessels,  and  furnished  with  a  black  pigment, 
called  \\iepigmentum  nigrum. 

Emily. — Is  the  white  of  the  eye  a  portion  of  the  scle- 
rotic coat  ? 

Dr.  B. — There  indeed,  you  do  not  see  the  sclerotic 
coat,  because  it  is  covered  by  a  reflection  of  mucous 
membrane,  called  the  conjunctiva.  If  this  were  stripped 
off,  we  should  then  see  the  sclerotic  coat.  The  sclerotic 
coat  does  not  completely  encircle  the  eye  ;  for  the  ante- 
rior portion  of  the  eye  is  bounded  by  another  coat,  called 
the  cornea.  Its  edges  are  intimately  connected  with 
those  of  the  sclerotic  ;  it  is  the  segment  of  a  smaller 
sphere ;  and  is  perfectly  colourless,  and  transparent. 

Emily. — Colorless  !  why  I  supposed  it  was  this  col- 
oured portion  in  the  middle  of  the  eye-ball.  I  cannot 
conceive  what  else  it  can  be,  for  there  is  no  other  part 
that  lean  see. 

Dr.  B. — The  part  which  gives  the  colour  to  the  eye, 
is  a  circular  membrane,  whose  edges  are  connected  with 
the  edges  of  the  cornea,  and  which  stretches  across  this 
portion  of  the  eye  like  a  curtain. 


HUMORS    OF    THE    EYE.  157 

Emily. — The  cornea  then,  is  in  front  of  this  mem- 
brane, and  of  course  a  space  must  be  left  between  them. 
But  what  do  you  call  it  ? 

Dr.  B. — It  is  called  the  iris,  and  is  the  seat  of  the 
colour  of  the  eye,  which  varies  you  know,  by  infinite 
shades,  in  different  individuals. 

Emily. — If  I  understand  it  right,  the  iris  has  a  hole  in 
its  centre,  forming  the  pupil,  as  it  is  called  ;  so  that  the 
shape  of  the  iris  is  that  of  a  flat  ring. 

Dr.  B. — It  is  through  the  pupil  that  the  rays  pass  ; 
if  the  iris  was  not  perforated  in  this  manner,  you  see 
they  would  be  entirely  intercepted.  The  iris  has  also 
the  power  of  contracting  and  dilating,  and  by  thus  in- 
creasing or  diminishing  the  diameter  of  the  pupil,  can 
accommodate  the  eye  to  the  various  changes  in  the  in- 
tensity of  the  light. 

Emily. — But  what  fills  up  the  space  that  is  left  be- 
tween the  iris  and  cornea  ?  I  cannot  discern  anything, 
and  yet  I  should  hardly  think  it  would  be  left  entirely 
empty. 

Dr.  B. — It  is  filled  with  a  watery,  transparent  fluid, 
called  the  aqueous  humor.  This  space  is  called  the  an- 
terior chamber  of  the  eye — that  behind  the  iris  is  called 
the  posterior  chamber.  The  first  thing  we  meet  with  in 
this  latter  chamber,  is  a  small  hard  body  just  behind  the 
iris,  nearly  of  a  spherioral  shape,  and  is  called  the  crys- 
talline humor,  or  lens.  The  remaining  portion  of  this 
chamber  of  the  eye,  is  occupied  by  a  dense,  tenacious 
fluid,  called  the  vitreous  humor,  from  its  resemblance  to 
melted  glass. — This  finishes  the  description  of  the  first 
division  of  the  parts  of  the  eye, — the  two  others  are  soon 
dispatched.  Expanded  on  a  portion  of  the  choroid 
coat,  is  a  very  delicate  coat,  chiefly  composed  of  nerves, 
and  generally  considered  as  an  expansion  of  the  optic 
nerve.  It  is  called  the  retina,  and  constitutes  the  se- 
cond division  of  the  parts  of  the  eye.  The  third  em- 
braces only  the  optic  nerve,  which  issues  from  the  back 
part  of  the  eye,  enters  the  skull  through  a  hole  in  the 


158 


OPTICAL    PRINCIPLES. 


orbit,  runs  along  the  base  of  the  brain,  and  terminates  at 
last  in  the  medulla  oblongata. 

Emily. — May  not  your  description  be  illustrated  by 
a  plate  of  the  eye  ?  This  would  now  give  me  a  very 
definite  notion  of  the  form  and  situation  of  the  several 
parts.  O,  here,  you  have  one  already. 

Dr.  B. — This  may  convey 
a  clearer  idea  of  the  matter 
than  mere  verbal  description. 
It  represents  a  vertical  sec- 
tion of  the  eye  in  the  middle. 
The  external  line  shows  the 
cut  edges  of  the  sclerotic  and 
the  white  one  within  it  of  the 
choroid  coat ;  in  front  you  see 
the  edge  of  the  cornea  ap- 
pearing like  a  sudden  bulge 
of  the  sclerotic.  At  a  little 
distance  behind  the  cornea  is  the  iris ;  and  between  it 
and  the  cornea  is  the  aqueous  humor.  Behind  the  iris 
you  observe  a  white  body,  representing  the  crystalline 
lens,  and  the  rest  of  the  chamber  is  occupied  by  the  vitre- 
ous humor.  At  the  posterior  portion  of  the  eye,  you 
may  see  the  commencement  of  the  optic  nerve. 

Emily. — This  is  quite  clear.  I  think  I  understand  now 
the  structure  of  the  eye  sufficiently  to  comprehend  the 
uses  and  actions  of  its  different  parts. 

Dr.  B. — If  you  have  any  wish  to  examine  the  eye 
itself,  it  is  easy  enough  to  procure  one  of  an  ox,  or  sheep, 
or  fish,  from  the  butchers,  and  by  first  freezing  it,  you 
may  cut  it  open  in  various  directions,  and  observe  all  its 
parts  very  satisfactorily. 

Emily. — I  should  be  delighted  to  examine  one  in  this 
way,  and  will  take  the  first  opportunity  to  procure  one. 
Dr.  /?.— Before  we  can  examine  the  functions  of  the 
several  parts  of  the  eye,  I  must  call  to  your  recollection 
a  few  of  the  most  prominent  principles  of  optics,  or  the 
laws  which  regulate  the  transmission  of  light.  Rays  oi 


PASSAGE  OF  THE  RAYS  THROUGH  THE  EYE.       159 


light  you  know,  in  passing  from  one  medium  to  anoth- 
er of  a  different  density,  are  always  refracted,  or  bent 
out  of  their  direction.  If  they  pass  from  a  denser  to  a 
rarer  medium,  as  represented  in 
this  figure,  where  the  horizontal 
black  line  represents  the  latter, 
the  space  above,  the  former  me- 
dium, and  the  oblique  line,  the 
ray  of  light,  they  are  refracted 
from  the  perpendicular.  But  in 
passing  from  a  rarer  to  a  denser 
medium,  the  contrary  takes  place. 
These  changes  happen  however,  only  when  the  rays 
fall  upon  the  surface  of  the  medium  obliquely ;  for  when 
they  fall  perpendicularly  to  it,  their  direction  is  not  chan- 
ged, whatever  may  be  the  difference  in  the  medium. 
You  must  bear  in  mind  too,  that  rays  of  light  proceeding 
from  a  luminous  object,  go  on  constantly  diverging ;  that 
this  divergency  is  increased,  by  suf- 
fering the  rays  to  pass  through  a  con- 
cave lens,  and  counteracted,  or  the 
rays  made  to  converge,  by  interpos- 
ing a  convex  lens.  The  next  two 
figures  will  illustrate  this  principle. 
Now  to  understand  how  the  rays  of 
f  \  light  are  modified  in  their  passage 

/  \         through   the  eye,    let  us  consider  a 

single  luminous  beam  falling  oblique- 
ly on  the  cornea.  In  entering  the 
cornea,  it  is  refracted  towards  the 
perpendicular  on  account  of  the  con- 
vexity of  this  part  ;  so  that  when 
rays  fall  on  every  point  of  the  sur- 
face of  the  cornea,  they  will  be  con- 
verged, and  thus  the  intensity  of  the 
light  be  increased. 

Emily. — And  in    traversing   the 
aqueous  humor,   this   being  denser 


160 


INVERSION    OF    THE    IMAGE. 


than  the  atmosphere,  the  beam  will  be  still  more  con- 
verged. But  what  becomes  of  the  rays  that  fall  on  the 
iris  ?  They  cannot  all  pass  through  the  pupil. 

Dr.  B. — Those  which  fall  on  the  iris  are  reflected 
back  through  the  aqueous  humor,  and  help  to  produce 
the  peculiar  lustre  of  the  eye. 

Emily. — They  have  now  to  pass  through  the  nearly 
spherical  crystalline  lens,  which  being  convex,  will,  I 
suppose,  still  farther  increase  the  convergency  of  the  rays. 
Dr.  B. — Yes ;  it  will  act  precisely  like  a  convex 
lens,  bringing  the  rays  sooner  to  a  focus,  in  their  passage 
through  the  vitreous  humor.  On  account  of  the  lesser 
density  of  the  latter  humor,  they  will  lose  a  little  of  their 
convergendy,  till  they  at  last,  fall  on  the  retina,  and 
there  form  the  image  of  the  object  from  which  they  pro- 
ceed. But  this  image  will  represent  the  object  in  an 
inverted  position — the  cause  of  which,  I  presume,  you 
will  not  need  my  aid  to  explain. 

Emily. — The  rays  which  enter  the  pupil  from  the 
upper  portion  of  the  cornea,  will  pass  on  in  a  downward 
direction,  and  fall  on  the  lower 
part  of  the  retina.  Those  entering 
it  from  below  will  take  an  upward 
direction,  crossing  the  others  in 
their  course,  and  fall  on  the  upper 
portion  of  the  retina,  while  the 
rays  which  pass  through  the  pupil 
perpendicularly  to  it,  will  strike 
on  the  centre  of  the  retina.  O, 
here  it  is  illustrated  in  this  figure. 
Dr.  B. — If  you  clearly  under- 
stand the  subject  so  far,  you  can, 
no  doubt,  readily  see  what  would 
be  the  effect  of  an  increase  of  the 
convexity  or  density  of  the  humors, 
on  the  image  of  the  object. 

Emily.— In   that  case,  I  sup- 
pose, the  rays  would   be  brought 


S&ORT-SIGHTEDNE9S.  161 

to  a  focus  sooner,  or  what  is  the  same  thing,  the  image 
would  be  formed  a  little  in  front  of  the  retina,  instead 
of  directly  upon  it. 

Dr.  B. — And  what  means  would  you  take  to  remedy 
it^  provided  such  an  affection  should  take  place  ? 

Emily. — I  am  sure  Dr.  B.,  I  cannot  tell  any  more 
than  the  man  in  the  moon.  I  suppose  physicians  make 
use  of  plasters  and  drugs,  whose  very  names  are  enough 
to  terrify  one. 

Dr.  B. — The  means  I  refer  to,  act  on  optical  prin- 
ciples, and  are  what  you  see  made  use  of  every  day. 
This  change  of  the  humors  takes  place  in  short  sighted 
people,  and  is  perfectly  well  remedied  by  using  concave 
spectacles. 

Emily. — These,  by  increasing  the  divergency  of  the 
rays,  will  counteract  the  undue  convergency  produced 
by  the  change  in  the  density  of  the  humors. 

Dr.  B. — If  on  the  contrary,  the  humors  are  not  suffi- 
ciently dense,  and  therefore  do  not  converge  the  rays 
enough,  the  focus  will  be  at  a  point  beyond  the  retina, 
and  the  image  will  be  very  indistinct.  This  affection  is 
peculiar  to  old  people. 

Emily. — And  is  corrected  by  using  convex  spectacles. 
I  never  imagined  before,  that  the  defect  of  vision  in  old 
and  young  people,  proceeded  from  precisely  opposite 
causes — the  one  from  too  little,  and  the  other,  from  too 
great  convergency  of  the  rays.  But  what  are  the  caus- 
es of  these  defects? 

Dr.  B. — The  former,  or  that  of  old  people,  seems 
to  be  the  natural  consequence  of  old  age,  though  some- 
times it  is  undoubtedly  brought  on  by  other  causes — 
that  of  being  accustomed  to  look  a  great,  deal  at  very 
distant  objects.  The  short  sightedness  of  young  people 
is  chiefly  produced  by  looking  at  objects  placed  too  near 
the  eye.  In  children,  it  frequently  is  a  consequence  of 
their  books  being  held  too  near.  I  knew  a  respectable 
school  where  short  sightedness  was  a  very  common  af- 
fection among  the  students,  by  reason  of  the  desks  beine; 
14* 


162 


SQUINTING. 


made  too  high — they  almost  touched  the  chins  of  the 
smaller  boys.  In  cases  of  this  kind,  the  defect  may  be 
easily  remedied  if  attended  to  in  season,  by  obliging  the 
child  to  look  frequently  at  distant  objects,  and  never 
permitting  him  to  hold  his  book  so  near  his  eyes  as  he 
generally  wishes. 

Emily. — How  is  it,  Dr.  B.,  that  the  eyes  are  able  to 
move  in  such  a  variety  of  directions,  and  move  too  so 
exactly  together,  as  always  to  be  directed  towards  the 
same  objects  ? 

Dr.  B. — It  is  by  the  aid  of  several  little  muscles,  that 
ihe  eyes  are  made  capable  of  every  possible  movement 
and  can  take  cognizance  of  ob- 
jects in  every  direction  not  abso- 
lutely behind.  These  muscles 
are  six  in  number ;  two  inserted 
into  the  superior,  two  into  the  in- 
ferior side  of  the  eye-ball.  These 
four  by  their  various  combina- 
tions of  actions,  roll  the  eye  in 
every  direction,  but  at  the  same 
time,  have  a  tendency  to  draw 
the  eye  backwards  a  little.  The 
two  others  counteract  this  ten- 
dency ;  one  of  them  as  you  will 
observe  in  this  figure,  produces 
this  effect  by  a  curious  arrange- 
ment. It  passes  through  a  loop  in  the  bone  in  advance 
of  the  level  of  the  eye,  and  of  course  draws  the  eye  for- 
ward, when  it  contracts.  When  both  eyes  are  turned 
in  precisely  the  same  direction,  the  image  is  formed  on 
corresponding  points  of  the  retina,  and  the  mind  per- 
ceives but  one  object.  When  however,  the  muscles  of 
the  eyes  contract  unequally,  we  observe  that  their  mo- 
tions do  not  correspond  ;  the  eyes  are  turned  in  differ- 
ent directions,  and  the  person  seems  to  be  looking  at 
two  objects. 

Emily. — This    then  constitutes  the  affection    called 


VISION    ASSISTED    BY    THE    OTHER    SENSES.       163 

squinting.  Why  should  not  those  who  squint,  behold 
two  objects  at  once  ?  It  is  certain  that  the  image  cannot 
be  formed  in  both  eyes,  on  corresponding  points  of  the 
retina,  and  you  observed  that  this  was  necessary  in  or- 
der that  the  mind  should  behold  but  one  object. 

Dr.  B. — Undoubtedly,  when  people  first  begin  to 
squint,  objects  do  appear  double,  but  the  mistake  being 
constantly  corrected,  the  mind  at  last  becomes  conscious 
of  beholding  but  one  object. 

Emily. — I  think  I  have  heard  that  the  sight  of  itself 
•alone,  gives  us  no  information  in  respect  to  the  distance 
of  objects,  but  that  this  is  the  result  of  habit  and  judge- 
ment. This  may  be  very  true,  but  I  confess,  I  do  not 
clearly  understand  it. 

Dr.  B. — Have  you  never  seen  a  young  babe  stretch 
out  its  hands  to  grasp  the  moon,  or  any  other  distant 
object  ?  To  people  also,  who  have  been  born  blind,  but 
received  their  sight  at  an  after  period  of  life,  objects  at 
a  mile's  distance,  appear  to  be  within  their  reach.  It  is 
by  the  long  habit  of  comparing  together  objects  at  dif- 
ferent distances,  that  we  judge  of  their  absolute  distance, 
and  not  by  any  original  power  of  the  eye.  When  we 
look  at  an  object  remote  from  others  with  which  we 
might  compare  it,  it  always  appears  much  nearer  to  us 
than  it  really  is.  Thus,  a  light  in  the  dark,  will  always 
appear  nearer  than  it  actually  is,  from  our  being  unable 
to  compare  it  with  intervening  objects.  It  is  the  same 
in  regard  to  the  size  of  objects  in  such  situations.  A 
man,  for  instance,  when  seen  from  the  top  of  a  high 
steeple,  will  seem  much  smaller  than  when  beheld  on 
the  same  level  with  ourselves  at  a  much  greater  distance. 

Emily. — I  have  noticed  this  fact,  but  it  never  occur- 
red to  me  that  it  was  owing  to  my  not  being  accustomed 
to  look  at  objects  in  a  vertical  direction. 

Dr.  B. — So  too,  the  eye  alone,  unassisted  by  the 
other  senses,  gives  us  no  knowledge  of  \heforms  of 
bodies.  Unaided  by  the  sense  of  touch,  all  objects 
would  present  the  appearance  of  a  flat,  uneven  surface. 


164       VISION    ASSISTED    BY    THE    OTHER    SENSES. 

When  we  look  at  a  round  body,  the  rays  oflight  proceed 
only  from  the  side  towards  us,  and  yet  we  never  are  in 
doubt  of  its  actual  form.  We  can  also  judge,  with  the 
same  degree  of  accuracy,  of  the  form  and  size  of  a  book 
at  ten  feet  distance,  as  at  one,  though  it  is  certain  that  in 
the  former  case,  the  image  of  the  object  on  the  retina  is 
much  smaller,  and  is  a  plain  figure.  Objects,  in  fact, 
are  represented  on  the  retina,  in  the  same  manner  as  in 
a  painting,  where,  whatever  may  be  their  size  or  figure, 
they  are  made  with  one  dimension  only  ;  so  that  to  a 
person  who  has  just  received  the  sense  of  sight,  external 
objects  appear  like  the  figures  in  a  painting  to  one — if 
we  can  suppose  such  an  one — wholly  ignorant  of  per- 
spective. 

Emily. — I  recollect  having  read  somewhere,  an  ac- 
count of  a  blind  person,  whose  sight  was  restored  by  an 
operation,  in  which  all  these  facts  in  regard  to  vision, 
were  very  pleasantly  illustrated.  I  have  forgotten  the 
details  of  the  account,  and  retain  only  a  general  impres- 
sion about  it. 

Dr.  B. — It  was  probably  the  one  told  with  delightful 
naivete  by  Cheselden,  a  distinguished  English  anatomist 
of  the  last  century,  and  is  quickly  related  : — 

"  When  he  first  saw,  he  was  so  far  from  making  any 
judgment  of  distances,  that  he  thought  all  objects  what- 
ever touched  his  eyes,  as  he  expressed  it,  as  what  he 
felt  did  his  skin  ;  and  thought  no  objects  so  agreeable 
as  those  which  were  smooth  and  regular,  though  he 
could  form  no  judgment  of  their  shape,  or  guess  what  it 
was  in  any  object,  that  was  pleasing  to  him.  He  knew 
not  the  shape  of  anything,  nor  any  one  thing  from  anoth- 
er, however  different  in  shape  and  magnitude.  Upon 
being  told  what  things  were,  whose  forms  he  before 
knew  by  feeling,  he  would  carefully  observe  them  that 
he  might  know  them  again  ;  but  having  too  many  ob- 
jects to  learn  at  once,  he  forgot  many  of  them,  and,  as 
he  said,  at  first  he  learned  to  know,  and  then  forgot  a 
thousand  things  in  a  day.  One  particular  only,  though 


VISION    ASSISTED    BY    fHE    OTHER    SENSES.       165 

it  may  appear  trifling,  I  will  relate.  Having  often  for- 
gotten which  was  the  cat,  and  which  the  clog,  he  was 
ashamed  to  ask  ;  but  catching  the  cat,  which  he  knew 
by  feeling,  he  was  observed  to  look  steadfastly  at  her, 
and  then  setting  her  down,  said,  so  puss,  I  shall  know 
you  another  time.  He  was  very  much  surprised  that 
those  things  which  he  liked  best,  did  not  appear  most 
agreeable  to  his  eyes — expecting  those  persons  would 
appear  most  beautiful  whom  he  loved  most,  and  such 
things  to  be  most  agreeable  to  his  sight,  that  were  so  to 
his  taste.  We  thought  he  soon  knew  what  pictures  rep- 
resented, when  showed  to  him,  but  we  found  afterwards 
that  we  were  mistaken  ;  for  about  two  months  after  he 
was  couched,  he  discovered  that  they  represented  solid 
bodies,  when  to  that  time,  he  considered  them  as  party- 
coloured  planes,  or  surfaces  diversified  with  a  variety  of 
paint.  But  even  then  he  was  no  less  surprised,  expect- 
ing the  pictures  would  feel  like  the  things  they  represent- 
ed, and  was  amazed  when  he  found  those  parts,  which 
by  their  light  and  shadow  appeared  now  round  and  un- 
even, felt  only  flat  like  the  rest,  and  asked  which  was  the 
lying  sense,  feeling  or  seeing  ?  Being  shown  his  father's 
picture  in  a  locket  in  his  mother's  watch,  and  told  what 
it  was,  he  acknogwledged  a  likeness  but  was  vastly  sur- 
prised ;  asking  how  it  could  be,  that  a  large  face  could 
be  expressed  in  so  little  room,  and  saying  it  would  have 
seemed  as  impossible  to  him,  as  to  put  a  bushel  of  any 
thing  into  a  pint.  At  first  he  could  bear  but  very  little 
light,  and  the  things  he  saw  he  thought  extremely  large  ; 
but  upon  seeing  things  larger,  those  first  seen  he  con- 
ceived less.  He  never  was  able  to  imagine  any  lines 
beyond  the  bounds  he  saw ;  the  room  he  was  in,  he 
said,  he  knew  to  be  but  part  of  the  house,  yet  he  could 
not  conceive  that  the  whole  house  could  look  any  big- 
ger." 

Emily. — It  must  have  been  very  amusing  truly,  to 
have  seen  him  so  intently  examining  the  cat,  and  express- 
ing his  wonder  at  his  father's  picture. 


166  HEARING. 

Dr.  B. — The  same  facts  are  established  by  many 
other  similar  cases  which  have  been  observed  by  physi- 
cians and  surgeons,  but  it  would  be  unnecessary  to  men- 
tion them.  Among  the  inferior  animals,  the  eye  becomes 
more  simple  in  its  structure,  until  in  some  of  the  very 
lowest  orders,  it  ceases  to  exist  entirely.  In  some  classes 
we  see,  the  structure  of  the  eye  is  modified  according  to 
the  medium  in  which  the  animal  lives.  Thus,  in  Birds 
the  anterior  portion  is  remarkably  convex,  because  the 
rays  of  light  passing  through  the  rarer  portions  of  the  at- 
mosphere, suffer  greater  divergency,  and  consequently 
the  eye  must  possess  a  corresponding  power  of  conver- 
gency.  In  Fishes,  on  the  contrary,  the  eye  is  very  flat, 
because  the  rays  before  they  reach  the  eye,  pass  through 
the  water  which  is  a  much  denser  medium  than  the  air. 
There  is  a  curious  form  of  the  eye  existing  in  the  Insect 
tribe,  called  the  compound  eye.  These  animals  possess 
two,  apparently  single,  eyes  in  their  head  ;  but  when  ex- 
amined by  a  microscope,  they  are  found  to  be  composed 
of  an  aggregate  of  a  vast  number  of  single  eyes  ;  or 
rather  the  external  coat  which  corresponds  to  the  cornea, 
is  made  up  of  these  numerous  six-sided  figures.  Every 
one  of  these  is  undoubtedly  furnished  with  a  nerve,  and 
is  in  fact,  a  perfect  eye.  In  the  eye  of  a  common  house- 
fly there  have  been  counted  8000.  In  Spiders,  the 
eyes  are  single  and  are  six  or  eight  in  number,  placed  in 
different  parts  of  their  body. 

Emily. — They  then  literally  share  with  man  the  priv- 
ilege of  "  looking  before  and  after."  Their  enemies  are 
so  numerous  however,  that  they  must  really  need  it. 

Dr.  B. — The  next  sense  to  which  we  shall  turn  our 
attention,  is  that  of  hearing.  This  sense,  briefly  defined, 
is  the  one  which  makes  us  acquainted  with  the  impres- 
sions of  sound;  and  sound,  you  know,  is  the  result  of 
motions  communicated  to  elastic  fluids  by  the  vibrations 
of  solid  bodies.  The  organ  of  hearing  is  an  apparatus 
most  admirably  contrived,  for  collecting  sounds,  and 
producing  the  requisite  impression  on  the  nerves,  which 


ANATOMY    OF    THE    fiAR  167 

communicate  them  to  the  brain.  No  part  of  the  human 
structure,  however,  is  so  complicated,  and  so  difficult  to 
be  comprehended  by  one  who  has  never  personally  ex- 
amined it,  as  the  ear.  For  this  reason  I  shall  not  per- 
plex your  mind  with  much  of  its  minute  anatomy,  since 
the  clearest  descriptions  in  the  world,  even  if  assisted  by 
plates,  would  fail  to  give  any  thing  like  an  adequate  con- 
ception of  it.  The  external  ear  is  composed  of  an  elas- 
tic cartilaginous  substance,  which  collects  the  sonorous 
rays,  and  may  be  compared  to  the  large  extremity  of  a 
trumpet.  Thence  the  sounds  are  transmitted  through 
the  auditory  canal  which  winds  along  in  the  substance 
of  the  bone.  At  its  termination,  there  is  stretched  di- 
rectly across  it  a  thin  tense  membrane,  called  the  mem- 
brane of  the  tympanum,  or  drum  of  the  ear.  On  ,  the 
other  side  of  this  membrane,  is  a  cavity  called  the  tym- 
panum, in  which  is  contained  a  chain  of  four  very  small 
bones,  connected  with  the  drum  of  the  ear  and  the  op- 
posite sides  of  the  cavity.  An  opening  into  the  pha- 
rynx, establishes  a  free  communication  with  the  air. 
Various  canals  and  cavities,  closed  by  tense  membranes, 
lead  from  the  tympanum,  containing  fluids,  in  which  are 
expanded  the  soft  and  delicate  filaments  of  the  auditory 
nerve.  This  is  enough  of  the  anatomy  of  the  ear,  for 
you  to  understand  how  the  vibrations  are  communicated 
to  the  nerve. 

The  membrane  of  the  tympanum  on  which  sounds 
first  strike  after  passing  through  the  external  auditory 
opening,  may  be  compared  to  the  head  of  a  drum,  and 
the  cavity  of  the  tympanum  being  supplied  with  air, 
serves  to  complete  the  resemblance  to  that  instrument. 

Emily. — The  use  of  the  Eustachian  tube,  then,  is  to 
supply  the  cavity  of  the  tympanum  with  air — but  why 
is  this  necessary  ? 

Dr.  B. — The  necessity  of  such  a  supply  of  air  will 
appear  very  obvious,  if  you  consider  thrt  if  a  drum  be 
exhausted  of  its  air,  no  sound  would  be  produced. 
Whether  the  membrane  of  the  tympanum  be  under  the 


1G8        HEARING    AIDED    BY    THE    OTHER   SENSES. 

control  of  any  muscles  by  which  it  is  relaxed  or  made 
tense,  according  to  the  graveness  or  acuteness  of  the 
sounds,  as  has  been  conjectured,  is  a  fact  on  which  we 
have  no  positive  information.  Vibrations  are  produced 
in  the  chain  of  small  bones,  and  in  the  walls  of  the  tym- 
panum, and  thence  transmitted  to  the  auditory  nerve. 
The  essential  part  of  the  organ  of  hearing,  is  the  cavity 
containing  the  soft  pulp,  in  which  the  auditory  nerve  is 
distributed.  This  is  found  wherever  the  sense  exists, 
and  where  none  of  the  other  parts  are  present,  as  in 
some  of  the  lower  orders  of  animals. 

Emily. — And  is  this  sense,  Dr.  B.,  as  much  under 
the  influence  of  habit,  as  that  of  sight  ? 

Dr.  B. — Certainly  ;  hearing  makes  us  acquainted 
only  with  the  existence  of  sounds — our  knowledge  of 
their  distance,  direction  and  nature,  is  obtained  by  ex- 
perience, and  the  assistance  of  the  other  senses.  Our 
knowledge  of  their  direction,  seems  to  depend  chiefly  on 
the  harmony  existing  between  both  ears.  If  we  close 
one  ear,  and  a  noise  be  made  at  a  little  distance  from 
us,  it  is  often  impossible  to  determine  whence  it  comes, 
though  with  both  ears  open,  we  might  not  be  at  any  loss 
to  determine.  We  are  considerably  assisted  also  in  our 
judgment  of  the  direction  of  sounds,  by  the  sight,  for  in 
the  dark,  we  often  find  it  very  difficult  to  tell  from  what 
point  it  comes.  We  judge  of  the  distance  of  sounds  too, 
by  having  been  long  familiar  with  them,  and  by  fre- 
quently comparing  them  together. 

Emily. — I  am  conscious  how  liable  we  are  to  be  de- 
ceived respecting  the  direction  and  distance  of  strange 
sounds — I  have  often  been  deceived  in  this  way,  my- 
self. .  Do  we  not  judge  of  the  distance  of  some  sounds 
also,  by  their  peculiar  tone,  and  when  this  tone  is  imi- 
tated, are  we  not  easily  deceived  ? 

Dr.  B. — Of  a  truth  we  are,  and  this  is  the  secret  of 
the  ventriloquist's  deception, — but  more  of  that  by-and- 

b>'- 

Emily. — Cannot  some  people  perceive  certain  sounds 


HEARING  IN  FISHES.  169 

which  are  entirely  inaudible  to  others,  whose  hearing  is 
nevertheless  acute  enough  in  regard  to  common  sounds  ? 
Dr.  B. — Yes,  there  are  a  few  sounds  of  this  kind, 
but  they  are  all  extremely  low. — Different  sounds  have 
the  power  of  affecting  the  ear — that  is,  the  physical  or- 
gans, agreeably  or  disagreeably.  The  harsh  grating  of 
metals  or  other  hard  bodies  on  one  another,  is  offensive 
to  every  ear ;  the  bubbling  of  a  brook,  and  the  song  of 
birds,  are  on  the  contrary,  agreeable  to  all.  The  sensa- 
tion is  also  greatly  modified  by  the  manner  in  which 
sounds  are  combined.  Sounds  made  from  musical  in- 
struments at  random  by  the  unskilled  and  ignorant,  are 
always  unpleasing ;  but  when  arranged  in  a  certain  or- 
der, and  directed  by  skill  and  taste,  they  are  a  source  of 
the  most  delightful  sensations. 

Emily. — What  is  the  cause  of  the  great  difference 
that  exists  among  people,  in  regard  to  the  manner  in 
which  they  are  affected  by  musical  sounds  ?  Is  it  any 
difference  in  the  structure  of  the  ear  ?  We  hear  of  peo- 
ple having  a.  good  ear,  and  a  bad  ear  for  music* 

Dr.  B. — This  language  is  literally  incorrect, — people 
have  confounded  that  mere  physical  delight  which  some 
sounds  will  produce  in  every  one,  with  that  internal  sat- 
isfaction which  arises  from  the  perception  of  harmony 
between  musical  sounds.  The  former  is  altogether 
physical,  like  the  pleasure  derived  from  the  sense  of 
smell  and  taste  ;  but  the  latter  originates  from  a  distinct 
faculty  of  the  mind,  which,  like  those  that  give  an  ex- 
cellence to  some  in  poetry,  painting  and  other  arts,  is  a 
gift  of  nature  not  bestowed  on  all. 

In  examining  the  oigan  in  the  inferior  animals,  we  see 
its  different  parts  vanishing  one  after  another,  until  we 
come  to  some  of  the  shell-fishes,  where  we  find  neither 
external  ear,  tympanum,  nor  bones,  but  merely  some 
membranous  sacs,  in  which  are  expanded  the  minute 
filaments  of  the  auditory  nerve.  Fishes,  and  some  rep- 
tiles have  no  external  passage  to  the  ear ;  the  only  com- 
munication is  by  the  Eustachian  tube. 
15 


170 


SMELLING, 


Emily. — But,  Dr.  B.,  do  fishes  possess  the  organ  of 

hearing  ? 

Dr.  B. — Fishes  probably  surpass  all  other  animals 
in  acuteness  of  hearing ;  owing  in  some  measure  per- 
haps, to  the  nature  of  the  medium  through  which  the 
vibrations  are  conveyed.  Water,  you  know,  must  be  a 
much  better  medium  for  conveying  sounds,  than  air. 
Some  few  fishes,  in  fact,  possess  the  rudiments  of  an 
external  ear. 

Emily. — Some  of  the  inferior  animals  have  one  ad- 
vantage over  us,  in  the  structure  of  their  hearing  organs. 
They  can  change  the  position  of  their  external  ear,  so 
as  to  correspond  to  the  direction  whence  the  sound  pro- 
ceeds. This  is  particularly  manifest  in  the  horse,  rab- 
bit, &c.,  and  these  animals,  if  1  mistake  not,  have  the 
sense  of  hearing  extremely  acute. 

Dr.  B. — Of  the  remaining  senses,  we  have  but  little 
to  say,  as  the  organs  are  extremely  simple,  and  their 
functions  can  be  observed  by  all.  Smelling  is  the  sen  e 
which  makes  us  acquainted  with  the  presence  of  certain 
particles  given  off  and  diffused  to  various  distances,  from 
odorous  bodies.  "  The  smelling  apparatus  may  be  com- 
pared to  a  sieve  placed  in  a  spot,  over  which  the  current 
of  air  that  is  introduced  into  the  chest  in  respiration, 
passes,  and  which  is  destined  to  detain  all  the  foreign 
bodies  which  may  happen  to  be  mixed  with  the  air,  par- 
ticularly odours.  This  apparatus,  in  the  first  place  con- 
sists of  the  pituitary  membrane,  which  lines  the  back 
part  of  the  nostrils  and  other  cavities  which  communicate 
with  them."  On  this  membrane,  are  distributed  the  mi- 
nute and  numberless  ramifications  of  the  olfactory  nerve, 
or  the  nerve  of  smell.  By  this,  the  impressions  made 
on  the  membrane,  are  communicated  to  the  brain.  In 
order  to  protect  this  delicate  expansion  of  nerves  thus 
freely  exposed  to  the  air  and  to  the  painful  stimulus  of 
acrid  and  pungent  odours,  the  membrane  is  kept  con- 
stantly moist  by  a  secretion  of  mucous  ftuid  from  the 
glands,  with  which  it  is  provided.  The  sense  of  smell 


SMELLING    OF    THE    INFERIOR    ANIMALS.          171 

is  one  of  quite  inferior  importance  in  the  animal  economy 
of  man.  It  furnishes  the  mind  with  few  ideas,  and  those 
are  subservient  exclusively  to  his  physical  nature. 

Emily. — I  have  known  several  persons  who  never 
possessed  the  sense  of  smell,  and  I  did  not  see  that  they 
suffered  any  material  inconvenience  from  the  want  of  it. 
Though  they  were  insensible  to  some  very  pleasant  sen- 
sations, they  were  at.  the  same  time,  spared  the  pain  of 
many  disagreeable  ones.  In  short,  I  do  not  see  but  that 
it  might  very  easily  be  dispensed  with. 

Dr.  B. — You  are  now  giving  it  a  lower  rank  than  it 
actually  deserves.  In  the  savage  state  of  man,  it  no 
doubt  furnishes  him  with  very  useful  hints  in  regard  to 
his  food,  but  now  its  natural  acuteness  is  weakened  and 
perverted  by  the  refinements  of  artificial  life.  But  as  it 
is,  we  often  reject  an  article  of  food,  if  unpleasant  to  the 
smell,  without  waiting  for  the  opinion  of  the  taste  to  con- 
firm our  decision.  Who,  after  smelling  tobacco,  or  hen- 
bane for  the  first  time  in  his  life,  would  ever  think  of 
tasting  it  ? 

Emily. — Sometimes  this  sense  seems  to  possess  a 
morbid  degree  of  acuteness  in  respect  to  some  odours, 
which  is  highly  inconvenient  and  even  dangerous.  I 
have  heard  of  persons  who  were  always  thrown  into 
convulsions  at  the  smell  of  cheese,  certain  fruits,  flowers, 
&c-  The  sense  of  smell  is  much  more  acute  in  some 
of  the  inferior  animals  than  in  man,  is  it  not  ? 

Dr.  B. — In  brute  animals  generally,  the  sense  exists 
in  greater  perfection,  than  in  man  ;  and  it  is  by  this 
sense  that  they  distinguish  with  such  wonderful  accuracy 
the  food  provided  for  them  by  nature,  and  know  how 
to  choose  between  the  evil  and  the  good.  Though  con- 
stantly feeding  among  noxious  vegetables,  they  are  sel- 
dom deceived,  but  select  from  the  poison  around  them, 
pleasant  and  wholesome  nutriment.-  In  some  of  the 
higher  orders,  there  is  an  astonishing  aeuteness  of  the 
smell  in  regard  to  the  effluvia  that  come  from  living 


172  TASTE. 

/ 

animals.  By  thus  making  them  acquainted  with  the 
presence  of  their  enemies  or  their  prey,  when  the  eye 
and  ear  are  incapable  of  acting,  it  possesses  an  impor- 
tance in  them,  far  beyond  what  it  has  in  man.  A  trav- 
eller in  Africa  relates,  that  they  were  always  apprized 
of  lions  being  in  their  vicinity  during  the  night,  by  the 
moans  and  trembling  of  their  horses. 

Emily. — 1  have  read  too,  that  the  American  bison  will 
snuff  the  effluvia  of  man,  for  the  distance  of  many  miles. 
And  think  how  accurately  a  dog  will  track  his  master 
merely  by  his  scent. 

Dr.  B. — Spurzheim  mentions  one  which  followed  his 
master  through  several  countries  in  Europe. 

Emily. — How  does  the  sense  exist  in  the  lower  orders 
of  animals— the  Fishes,  for  instance. 

Dr.  B.— Fishes  possess  it  in  a  remarkable  degree  of 
acuteness.  This  is  well  manifested  in  the  nicety  they 
exhibit  in  regard  to  different  baits  employed  in  taking 
them.  Thus,  a  worm  that  has  lost  its  flavor  by  long 
maceration  in  water,  will  be  refused  by  a  fish  ;  but  the 
same  worm,  after  having  its  odour  revived  by  fresh  in- 
cisions made  into  it,  will  be  taken  greedily.  In  the  or-^ 
ders  still  lower,  the  sense  is  quite  obscure,  and  we  know 
but  little  about  it. — We  must  now  consider  the  sense  of 
Taste,  and  so  simple  is  its  nature,  that  I  presume  you 
can  easily  define  it  yourself. 

Emily. — It  is  the  sense  which  makes  us  acquainted 
with  the  impressions  produced  on  the  tongue  by  sapid 
bodies.,  There— am  I  correct  ? 

Dr.  B, — The  tongue  is  the  principle  organ  indeed, 
but  the  sense  is  possessed  in  some  degree  by  the  lips, 
sides  of  the  cheek,  and  palate.  These  parts  are  all 
abundantly  provided  with  vessels  and  nerves  which  are 
expanded  beneath  the  lining  membrane,  and  form  little 
eminences  called  nervous  papilla.  These  are  the  seat 
of  the  impressions,  which  are  transmitted  from  them  to 
the  brain.  In  order  that  the  sense  may  be  perfectly 


TASTE  OP  THE  INFERIOR  ANIMALS.  173 

exercised,  the  mouth  must  be  constantly  supplied  with 
saliva,  and  the  other  secreted  fluids.  In  fevers  and  oth- 
er diseases  in  which  the  secretions  are  changed,  this 
sense  is  always  imperfect  and  vitiated.  Placed  thus  at 
the  entrance  of  the  alimentary  canal,  all  our  food  is  first 
subjected  to  its  scrutiny,  before  it  is  conveyed  to  the 
digestive  organs.  No  sense  has  been  made  to  vary  so 
much  by  the  refinements  of  social  life,  as  that  of  Taste. 
The  taste  of  wild  animals  and  of  savage  man,  is  the  same 
in  all  individuals  of  the  same  species — they  all  probably, 
like  or  dislike  the  same  food.  But  among  civilized  men, 
no  two  individuals  can  be  found  alike  in  all  their  tastes ; 
and  so  general  and  well  understood  is  this  diversity,  that 
one  would  as  soon  think  of  disputing  another's  conscience, 
as  his  taste. 

This  sense  may  be  considerably  improved  in  acute- 
ness,  by  long  training.  Those  whose  business  requires 
them  to  judge  of  the  qualities  of  objects  by  their  taste, 
acquire  in  time  a  nicety  of  this  sense,  which  is  incon- 
ceivable to  others.  The  acuteness  of  taste  in  different 
persons,  varies  according  to  the  sapid  bodies  themselves  : 
some,  very  readily  tasting  what  others  do  not. 

Emily. — This  fact,  I  recollect  is  very  pleasantly  illus- 
trated in  Don  Quixote,  by  the  story  of  two  wiseacres 
who  were  tasting  wine.  One  thought  the  wine  tasted — 
a  little — of  leather  ;  the  other  was  very  confident,  that 
he  tasted — iron.  The  wine  was  at  last  drank  up,  when 
looking  into  the  vessel,  lo !  there  was  found  an  iron  key 
with  a  leathern  thong  attached  to  it. 

Dr.  B. — The  taste  grows  imperfect  in  the  Birds,  be- 
comes still  more  so  in  the  Reptiles,  and  is  entirely  want- 
ing in  the  Fishes,  and  other  animals. 

Emily. — How  is  this  fact  known  in  regard  to  Fishes  ? 

Dr.  B. — It  is  inferred   from  the  structure  of  their 

mouth,   and  from  the  indiscriminate  manner  in  which 

they  swallow  any  thing  that  has  the  appearance  of  prey. 

A  mackerel  will  swallow  a  piece  of  red  flannel,  with  as 

15* 


174  COLOUR    OF    THE 

much  avidity  as  any  other  bait,  and  in  sharks  there  have 
often  been  found  ballast-stones,  marling-spikes,  hatchets, 
and  similar  articles.  Besides,  owing  to  the  sameness  of 
their  food,  and  consequently,  the  little  necessity  of  dis- 
crimination, this  sense  was  obviously  not  required. — 
But  we  must  conclude  our  account  of  the  senses,  with 
the  last  and  most  general  of  all,  that  o(  Touch. 

Emily. — This  sense  makes  us  acquainted  with  a  great 
variety  of  the  physical  properties  of  bodies,  form,  dimen- 
sion, consistence,  smoothness,  motion,  &tc.  Its  seat 
seems  to  be  as  general  as  its  powers — being  the  whole 
surface  of  the  body. 

Dr.  B. — The  sense  of  touch  must  not  be  confounded 
with  that  of  mere  feeling  which  merely  apprizes  us  of 
the  contact  of  foreign  bodies,  without  giving  us  very 
definite  ideas  of  their  qualities.  However^  the  former 
seems  to  be  only  a  more  perfect  kind  of  the  latter,  and 
the  seat  of  both  is  near  the  surface  of  the  body  within 
its  integuments.  These  integuments,  included  under 
the  general  term  of  skin,  are  described  by  anatomists  as 
composed  of  several  distinct  strata  or  layers,  different  in 
appearance  and  name.  The  most  internal,  that  which 
constitutes  the  chief  bulk  of  the  skin,  is  called  the  Der- 
mis,  or  true  skin.  It  is  strong  and  compact  in  its  texture 
and  chiefly  composed  of  countless  myriads  of  minute- 
arteries,  veins,  nerves,  &c.  which  traverse  it  in  every 
direction.  From  the  nerves  which  are  distributed  over 
every  point  of  its  surface,  it  receives  that  acute  and  del- 
icate sensibility  which  renders  it  preeminently  fitted  to 
be  the  organ  of  touch  and  feeling.  Its  colour  is  very 
nearly  the  same  in  all  the  varieties  of  the  race,  and  de- 
pends entirely  on  the  state  of  the  minute  blood-vessels.. 
*'  According  as  they  are  full  or  empty,  it  may  vary  (as 
we  see  it  in  the  white  races)  from  a  more  or  less  florid 
red,  constituting  what  artists  call  flesh-colour,  to  the  waxy 
of  fainting,  or  exhaustion  frona  hemorrhage,.'- 


RETE    MUCOSUAl,  175 

Emily. — Do  you  really  mean  that  the  colour  of  the 
skin  is  the  same  in  all  mankind  ?  If  such  is  the  case, 
why  then  I  have  always  been  in  an  error  respecting  the 
seat  oi  colour.  Does  not  the  poet  speak  of  a  fellow-being 
having  a  "  skin  not  coloured  like  my  own"  ? 

Dr.  B. — Yes — but  neither  poets,  nor  any  other  per- 
sons are  bound,  in  the  iamiliar  use  of  words,  to  adhere 
to  their  strict  anatomical  meaning.  The  seat  of  colour 
is  not  in  the  true  skin,  but  in  another  part  which  we 
shall  describe  presently. 

The  external  layer  of  the  integuments,  or  epidermis, 
as  it  is  called — which  is  very  well  seen  when  raised  by 
a  blister — is  formed  by  minute  scales  lapping  over  each 
other,  as  in  the  skin  of  a  fish.  From  their  extreme 
minuteness,  this  structure  is  visible  only  under  a  power- 
ful microscope.  It  is  said  to  be  furnished  with  neither 
blood-vessels,  absorbents,  nor  nerves,  and  its  only  use 
seems  to  be  to  afford  protection  to  the  more  delicate' 
parts  beneath.  Its  colour  is  nearly  alike  in  the  fair  as 
well  as  dark  coloured  races,  but  it  is  generally  a  little 
deepened  by  exposure  to  the  rays  of  the  sun. 

Between  these  two  layers,  we  find  one  still  more  del- 
icate, called  the  rete  mucosum.  Its  nature  is  very  im- 
perfectly known  ;  it  is  not  decided  whether  it  be  an 
extremely  fine  net-work  of  capillary  vessels,  filled  with 
variously  colored  fluids,  or  merely  an  unorganised  pulp* 
This  layer  has  never  yet  been  discovered  in  the  white 
races,  though  there  can  be  little  doubt  that  it  does  exist, 
and  that  it  is  in  consequence  of  its  extreme  delicacy 
alone,  that  it  has  eluded  observation, 

Emily. — Why  should  it  be  so  much  more  easily  dis- 
covered in  the  Negro,  than  in  white  people  ? 

Dr.  B. — Because,  in  the  former  it  is  of  a  black  color  ? 
and  is  perhaps  thicker,  though  it  is  so  extremely  thin 
and  delicate  that  no  small  nicety  of  dissection  is  requi- 
site, in  order  to  find  it.  When  removed  and  placed  in 
water,  it  diffuses  itself  ia  the  fluid,  and  gives  a  turbid 


1*76  SEAT  OP  COLOUR. 

cloud  to  it.  The  most  important  fact  however,  in  regard 
to  the  rete  mucosum  is,  that  it  is  the  seat  of  colour — of 
those  diversified  tints  which  characterise  the  various 
races  of  men. 

Emily. — But  is  its  colour  permanent — never  changed 
by  exposure  to  the  heat  of  the  sun  ? 

Dr.  B. — Never — but  generation  after  generation,  in 
this  climate  or  in  that,  it  is  the  same  ;  as  unalterable  as 
any  other  feature  of  the  human  structure. 

Emily. — Well,  I  always  supposed — indeed  I  have 
often  read  it  books  of  high  authority — that  the  colour  of 
the  body  depended  solely  on  the  action  of  the  sun's  rays, 
it  shades  being  deepened  according  to  the  intensity  of 
the  heat  and  light.  Negroes,  you  know,  live  in  the  tor- 
rid zone,  brunettes  in  temperate,  or  moderately  warm 
latitudes,  and  light  florid  complexions,  as  those  of  north- 
ern Europeans,  in  colder  climates. 

Dr.  B. — If  you  are  disposed  to  resort  to  facts,  and 
are  willing  to  examine  them  impartially,  you  will  find 
that  you  have  gone  to  the  wrong  source  to  find  proofs  of 
your  opinion,  for  they  afford  the  most  satisfactory  de- 
monstration of  its  incorrectness.  Some  blacks  do  indeed 
live  in  the  torrid  zone,  but  the  whole  continent  of  New- 
Holland,  the  southern  extremity  of  which  extends  to  the 
40°  of  south  latitude,  abounds  with  inhabitants  whose 
complexions  are  as  black  as  the  Negroes'.  In  the  polar 
regions,  men  instead  of  being  uncommonly  white,  as 
they  should  according  to  your  theory,  are  very  tawny. 
Throughout  the  whole  American  continent,  excepting 
the  arctic  regions,  the  copper  tint  prevails  with  very  lit- 
tle variation. 

Emily. — But  it  is  a  fact  that  Europeans  and  others 
who  have  been  educated  in  a  temperate  climate,  will  ac- 
quire a  deep  shade  of  brown  after  a  few  years'  residence 
in  hot  countries,  and  will  regain  their  original  tint  gen- 
erally, when  they  return  home.  Now  it  seems  very 
reasonable  to  believe  that  the  colour  of  the  black  races 


ALBINOS.  177 

has  been  acquired  by  long  exposure  to  the  action  of  in- 
tense heat  and  light. 

Dr.  B. — The  change  which  you  allude  to,  is  precisely 
like  that  called  tanning.  Its  effects  are  quite  superfi- 
cial and  temporary,  and  disappear  when  the  part  that 
experiences  the  change  is  renewed.  The  Moors  have 
lived  in  Africa  ever  since  the  seventh  century,  and  still 
their  children  are  born  as  fair  as  those  of  Europeans. 
The  Negroes  have  lived  in  the  New  World  more  than 
two  hundred  years,  and  their  color  is  as  black  as  ever. 
The  farther  we  go  into  the  examination  of  facts  on  this 
point,  the  stronger  will  be  the  confirmation  of  the  fact, 
that  the  human  complexion  is  independent  of  climate,  or 
in  truth  of  any  other  known  physical  cause. 

Emily. — I  acknowledge  myself  convinced  by  your 
proofs,  and  will  cheerfully  give  up  my  theory.  But  if 
the  rete  mucosum  as  you  call  it,  has  never  been  found  in 
white  people,  what  proof  is  there  that  it  does  really  exist  r 

Dr.  B. — -The  white  races  are  not  destitute  of  colour 
by  any  means ;  some  indeed,  are  quite  brown,  as  the 
Spaniards,  Greeks,  &c.  Now  if  the  rete  mucosum  is 
the  seat  of  colour  in  blacks,  there  is  good  reason  to  be- 
lieve that  it  is  also,  in  the  whites.  Besides,  there  are 
sometimes  born  among  the  blacks  and  other  dark-coloured 
people,  individuals  who  are  entirely  white,  but  it  is  a  col- 
our very  different  from  that  of  the  white  races.  It  is  a 
dirty  white  or  cream  colour,  and  the  skin  has  sometimes 
a  remarkable  roughness. 

Emily. — You  refer  now  to  the  Albinos,  do  you  not  ? 
I  had  the  pleasure  of  seeing  one  a  few  years  ago,  and 
not  only  was  the  complexion  unnaturally  white,  but  the 
hair  was  white,  or  rather  silvery,  and  the  eye-brows  and 
eye-lashes  were  of  the  same  tint.  The  iris  was  of  a  light 
rose  colour,  and  the  pupil  red.  What  is  the  cause  of  this 
strange  phenomenon  ?  I  have  understood  that  it  is  not 
unfrequent  among  the  negroes.  Humboldt  has  obser- 
ved it  among  the  South  American  Indians,  and  Dubois 
says  it  occurs  in  India. 


178  EXPERIMENTS    OF    HOME. 

Dr.  B. — It  is  owing  to  a  deficiency  of  the  rete  mu- 
cosum  which  contains  the  colouring  substance,  and  it 
sometimes  occurs  in  the  inferior  animals.  White  speci- 
mens have  been  found  of  the  rabbit,  ferret,  mouse,  wea- 
sel, fox,  bear,  beaver,  rhinoceros,  camel,  elephant,  buf- 
faloe ;  the  crow,  black-bird,  canary-bird,  partridge,  and 
a  great  many  more. 

Emily. — And  it  is  this  peculiar  appearance  of  the  skin 
when  the  rete  mucosum  is  known  to  be  absent,  which 
induces  you  to  think  that  it  may  be  present  in  the  white 
races,  and  be  the  seat  of  their  various  tints  ?  Well,  the 
argument  seems  to  be  sound,  and  for  want  of  a  better,  I 
will  adopt  your  opinion  for  the  present. 

I  should  like  to  know  however,  what  the  use  of  the 
black  rete  mucosum  can  be  to  the  Negroes ;  or,  if  any 
purpose  be  answered  by  it,  which  is  not  by  the  white 
one  of  other  people. 

Dr.  B. — Sir  Everard  Home  has  tried  some  experi- 
ments, the  result  of  which  proves  that  the  black  colour 
enables  them  to  resist,  in  a  remarkable  degree,  the  ra- 
diant heat  of  the  sun's  rays. 

Emily. — Pray,  what  were  these  experiments  ?  Black 
I  always  thought,  absorbed  heat,  and  of  course,  made 
the  body  hotter  over  which  it  is  placed. 

Dr.  B.— This  is  true  of  unorganized  matter,  but  not 
so  it  seems,  when  we  speak  of  this  colour  in  reference  to 
animal  bodies.  However,  I  will  relate  the  experiments, 
and  you  may  judge  for  yourself.  This  gentleman,  among 
other  experiments,  exposed  the  backs  of  his  two  hands 
to  the  sun's  rays,  with  a  thermometer  upon  each,  one 
hand  being  covered  by  a  piece  of  black  cloth  under 
which  the  back  of  the  thermometer  was  placed,  and  the 
other  being  freely  exposed  without  any  covering.  The 
result  was,  that  though  the  thermometer  under  the  cloth 
stood  four  or  five  degrees  higher,  than  the  other,  yet  in 
every  one  of  these  trials,  the  exposed  hand  was  scorched, 
while  the  other  did  not  suffer  in  the  slightest  degree. 

At  another  time,  when  the  thermometer   in   the  sun 


TOUCH1.  179 

was  at  90°,  the  concentrated  rays  were  applied  to  a 
piece  of  black  kerseymere,  made  tight  round  the  arm 
twelve  minutes,  without  giving  pain,  or  leaving  any  im- 
pression on  the  skin. 

Emily. — Did  not  the  cloth  in  this  case  serve  to  pro- 
tect the  skin,  and  would  not  the  same  result  have  fol- 
lowed, if  white  cloth  had  been  used  ? 

Dr.  B. — No  ;  for  the  experiment  was  repeated  with 
white  kerseymere,  the  heat  being  at  86°  ;  in  fifteen 
minutes,  a  blister  was  formed  and  coagulable  lymph 
thrown  out.  At  another  time,  a  white  handkerchief  * 
was  used,  loose  upon  the  hand,  and  an  inflammatory 
blush  was  produced  over  the  surface,  of  several  inches 
extent. 

Emily. — So,  then,  the  colour  of  the  negro  serves,  in 
a  measure,  to  protect  him  from  the  scorching  effects  of 
a  vertical  sun. 

Dr.  B. — But  we  must  drop  this  digression,  and  go 
back  to  the  sense  of  touch.  All  the  skin  is  endowed 
with  feeling  though  in  different  degrees ;  the  palms  of 
the  hands  and  soles  of  the  feet,  you  know  are  exceeding- 
ly sensible.  The  sense  seems  to  reside  more  immedi- 
ately in  the  cutaneous  papilla,  a  set  of  minute  bodies  to 
be  seen  on  the  surface  of  the  dermis,  and  composed  of 
blood-vessels  and  the  extremities  of  nerves.  The  touch 
resides  chiefly  in  the  hands,  whose  structure  eminently 
fits  them  for  this  function.  Their  integuments  are  thin 
and  flexible,  and  abundantly  supplied  with  nerves  and 
vessels.  The  motions  of  the  hands  are  likewise  free 
and  extensive,  and  by  means  of  the  fingers,  the  object 
is  touched  at  several  points  at  once. 

The  sense  of  touch  is  far  more  perfect  in  man,  than 
in  the  brutes,  and  has  often  been  considered  by  philos- 
ophers as  contributing  in  a  very  high  degree  to  his  eleva- 
tion in  the  scale  of  being. 

Emily. — BufTon,  I  believe,  even  thought  that  much 
of  the  difference  in  men's  minds  arose  from  the  differ- 
ent degrees  of  perfection  in  which  the  sense  is  possess- 


180  VOICE. 

ed,  and  considered  it  very  important,  that  infants  should 
be  allowed  the  free-use  of  their  hands. 

Dr.  B. — These  views  are  extremely  unphilosophical 
and  have  no  foundation  in  truth. 

Emily. — Do  hrutes  possess  this  sense  in  any  degree? 
It  seems  difficult  to  conceive  of  the  sense  of  touch,  with- 
out either  thumbs  or  fingers  to  exercise  it. 

Dr.  B. — Nevertheless,  it  may  and  actually  does  re- 
side to  a  certain  degree  of  perfection  in  other  parts.  In 
the  racoon,  it  exists  in  the  toes  of  the  fore  feet ;  in  the 
opossum,  it  is  evidently  exercised  by  the  tail ;  in  the 
horse,  ass,  and  ruminant  tribe,  it  is  quite  acute  in  the  lips 
and  tongue ;  in  the  elephant,  it  is  in  the  end  of  the 
trunk  ;  and  in  the  pig,  the  snout  is  the  organ  of  touch* 
In  the  bats,  the  skin  which  covers  the  ears,  wings, '&&., 
possesses  such  a  perfect  sense  of  touch,  that  when  flying 
along  in  the  air,  they  can  tell  by  the  difference  in  its  reac- 
tion, when  they  are  approaching  any  object. 

Emily. — And  they  will  fly  equally  well  after  they 
have  been  entirely  blinded,  according  to  some  experi- 
ments that  have  been  tried  on  them. 

Dr.  B. — We  must  now  turn  our  attention  to  the 
Fbice,  another  of  the  animal  functions.  Though  not  in- 
cluded among  the  senses,  it  is  of  no  less  importance  in 
enlarging  the  relations  of  the  animal  with  the  external 
world,  and  is  possessed  by  man  in  common  with  many 
of  the  inferior  animals, 

Emily. — Do  you  mean  seriously,  that  voice  is  pos- 
sessed by  brutes  ?  If  so,  I  have  never  been  so  fortunate 
as  to  hear  them  speak,  though  1  am  conscious  some  of 
their  speeches  are  recorded  in  Gay's  Fables,  and  sun- 
dry spelling-books. 

Dr.  B. — Your  pleasantry  all  happens  to  be  made  at 
your  own  expense  ;  for  you  have  mistaken  voice  for  lan- 
guage— two  very  different  things.  The  latter  refers  to 
articulate  sounds,  expressive  of  definite  ideas,  and  is  in- 
deed the  prerogative  of  man  ;  the  former  includes  ill 
sounds  made  when  the  air  passes  through  the  wind-pipe, 


LIGAMENTS    OF    THE    GLOTTIS.  181 

either  to  or  from  the  lungs,  and  is  possessed  by  all  ani- 
mals, and  those  only,  that  are  provided  with  lungs.  In 
this  figure,  you  see  the  trachea  surmounted  by  a 
sort  of  capacious  box,  formed  by 
thick  cartilaginous  walls.  This 
part  is  called  the  larynx,  or  organ 
of  voice.  It  is  this  which  forms 
the  prominence  in  the  front  of  the 
neck,  called  Adam's  apple. 

Emily. — What  a  whimsical 
name  for  an  organ  of  the  body. 
Pray,  what  did  it  originate  from : 
Dr.  B. — There  is  a  story 
recorded  by  some  of  the  old  an- 
atomists, that  when  Adam  swal- 
lowed the  apple,  it  stuck  in  his 
throat,  and  produced  this  prom- 
inence which  has  ever  since  been 
faithfully  transmitted  to  his  pos- 
terity. 

Emily. — A  fact  well  remem- 
bered, and  ought  to  be  borne  in 
mind  when  the  curiosity  of  our 
common  mother  is  made  the 
subject  of  wilicism. 

Dr.  B. — The  larynx  is  pro- 
vided with  a  number  of  muscles,  the  use  of  which  is  t0 
move  it  as  a  whole,  or  its  different  parts  on  one  another. 
It  opens  at  the  top  into  the  pharynx  by  a  longitudinal 
slit,  or  chink,  called  the  chink  of  the  glottis,  about  eight 
lines  in  length,'  and  two  or  three  in  width. 

Emily. — It  is  this  chink  which  is  covered  by  the  epig 
lottis,  and  is  closed  in  the  act  of  swallowing,  I  believe. 

Dr.  B. — The  same  ;  at  its  inferior  portion,  we  find 
the  two  broad  ligaments  stretching  across,  one  from  each 
side,  and  leaving  between,  a  longitudinal  slit  opposite  to, 
and  very  similar  to  that  of  the  glottis.  These  ligaments 
can  be  relaxed  or  made  tense,  and  are  set  into  rapid  vi- 
brations when  the  air  rushes  through  them. 
16 


}82  LARYNX    OF    THE    LOWER    ANIMALS. 

Such  is  the  structure  of  the  organ  of  voice  ;  yet,  simple 
as  it  is,  the  mechanism  of  this  function,  is  far  from  be- 
ing established.  It  is  agreed  on  all  hands,  that  the  voice 
is  formed  at  the  moment  when  the  air  traverses  the  lar- 
ynx, but  physiologists  are  not  agreed  as  to  the  part  which 
these  ligaments  act.  Some  have  supposed  that  while 
vibrating,  they  produce  sounds  like  the  strings  of  a  vio- 
lin, and  have  given  them  the  name  of  Vocal  Chords. 
Others  have  compared  them  to  the  reed  of  a  clarionet  ; 
while  some  have  supposed  that  the  sound  is  produced, 
not  by  the  vibrations  of  these  ligaments,  but  merely  by 
the  rushing  of  the  air  through  the  narrow  opening  of  the 
glottis  ;  by  these,  the  larynx  has  been  compared  to  a 
flute,  or  whistle. 

Emily. — The  truth  is,  I  suppose,  that  the  subject  is  a 
very  obscure  one,  and  every  one  who  speculates  upon 
it,  likes  his  own  theory  better  than  his  predecessors'. 
But  let  us  see  what  they  amount  to. 

Dr.  B. — We  cannot  enter  into  a  discussion  of  their 
merits,  for  it  would  lead  us  too  far  into  the  science  of 
sounds.  It  may  be  remarked,  merely,  that  it  is  certain, 
that  these  ligaments — the  vocal  chords — do  vibrate 
when  the  voice  is  produced,  and  that  they  either  pro- 
duce, or  essentially  affect  the  sound.  But  the  organ  of 
voice  cannot  be  called  a  flute,  a  violin,  nor  a  clarionet ; — 
it  is  a  larynx,  an  instrument  which  art  has  as  yet  but  im- 
perfectly imitated. 

Forming  now,  in  your  mind,  a  distinct  idea  of  the 
human  larynx,  you  will  readily  understand  the  points  of 
resemblance  and  difference  between  it  and  those  of  the 
inferior  animals.  Among  the  mammiferous  animals, 
there  is  not  one  whose  larynx  is  not  provided  with  the 
same  apparatus  as  man's  ;  while  in  many  we  find  parts 
which  he  has  not.  So  that  with  more  complicated  or- 
gans, most  of  these  animals  produce  only  inarticulate  and 
disagreeable  sounds. 

Emily. — If  then  their  larynx  is  formed  like  man's, 
how  are  we  to  account  for  their  inability  to  produce  ar- 


LARYNX  OF  THE  LOWER  ANIMALS.       1S3 

ticulate  sounds.     I  had  always  supposed  that  they  were 
destitute  of  some  parts  of  the  vocal  organs. 

Dr.  B. — All  we  can  say  about  the  matter  is,  that  the 
functions  of  voice  is  not  needed  by  them,  and  therefore 
they  are  not  provided  with  it, — they  can  gratify  all  their 
natural  wants,  and  fulfil  the  purposes  of  their  being  per- 
fectly well  without  it. 

In  some  of  the  apes,  the  vocal  organs  have  a  curious 
structure.  There  is  connected  with  the  larynx  a  bony, 
or  a  membranous  sac,  either  single  and  placed  in  the 
middle  of  the  neck*,  or  as  in  some  species  double,  one 
on  each  side  extending  the  whole  length  of  the  neck. 
From  these  sacs  there  is  always  a  free  communication 
with  the  cavity  of  the  larynx. 

Emily. — May  not  the  inability  of  uttering  sounds  in 
these  creatures,  be  attributed  to  this  arrangement  ?  Or 
is  it,  after  all,  solely  the  result  of  moral  causes  ? 

Dr.  B. — When  this  peculiarity  of  structure  was  first 
brought  to  light,  philosophers  thought  that  they  had 
found  out  for  certain,  the  true  reason  why  apes  do  not 
speak,  but  further  researches  proved  that  there  exists 
many  species  of  apes  in  which  this  peculiarity  is  not 
found ;  and  yet  they  are  just  as  destitute  of  the  art  of 
speech  as  the  others. 

Emily. — How  does  this  arrangement  effect  the  pro- 
duction of  sounds  in  these  animals  ? 

Dr.  B. — The  voice  of  those  with  the  bony  box,  is 
exceedingly  intense  and  disagreeable.  The  Alouatte 
and  Ouaririe,  two  species  in  South  America,  have  long 
attracted  the  attention  of  travellers  by  the  intensity  and 
harshness  of  their  cries,  and  hence  have  received  the 
name  of  Howlers.  "  Their  cry,  or  rather  horrible  rat- 
tling screams  which  they  make,  may  well  inspire  terror, 
and  seems  as  if  the  forests  contained  the  united  howlirigs 
of  all  its  savage  inhabitants  together." 

In  the  larynx  of  the  dog,  sheep,  cat,  ox,  &c.  we  find 
the  same  number  of  parts,  and  the  same  arrangement,  as 
in  man, — the  principal  difference  being  in  the  width  and 


184  VOICE    MODIFIED    BY    THE     SIZE    OF    THE    LARYNX. 

thickness  of  the  ligaments,  and  in  the  shape  of  the  epi- 
glottis. 

The  larynx  of  birds  differs  from  those  already  de- 
scribed chiefly  in  this,  that  they  have  no  epiglottis  and 
that  the  vocal  chords  and  proper  cavity  of  the  larynx  is 
in  the  chest — in  the  lower  part  of  the  wind-pipe,  just 
where  it  divides  into  the  bronchiae  to  go  to  the  lungs,  and 
the  chink  of  the  glottis  of  course  being  still  at  the  summit 
of  the  wind-pipe.  The  former  parts  have  been  called 
by  anatomists,  the  inferior  larynx  ;  the  latter  part,  the 
superior  larynx,  as  if  there  were  really  two  larynxes  in 
birds. 

Emily. — But  in  which  of  them,  pray,  is  the  voice 
formed  ? 

Dr.  B. — It  is  the  opinion  of  Cuvier  that  it  is  formed 
in  the  inferior  larynx  alone.  He  cut  off  the  wind-pipe 
of  a  black-bird  near  its  middle,  and  then  shook  him,  in 
the  same  way  as  he  would  have  done  to  make  him  cry  in 
the  natural  state.  His  cries  were  very  perceptible,  though 
much  more  feeble  than  before.  The  same  experiment 
was  performed  on  a  mag-pie, — it  continued  to  cry,  and 
its  cries  were  not  less  intense  than  in  its  natural  state. 

Emily. — I  have  heard  before  of  hens  and  turkeys  ut- 
tering hoarse  cries,  after  their  heads  were  cut  off,  but 
never  imagined  it  was  a  fact  observed  by  physiologists, 
and  explained  by  anatomical  reasons. 

Dr.  B. — This  structure  produces  a  remarkable  differ- 
ence between  the  voice  of  birds  and  other  animals.  In 
the  latter,  the  voice  being  formed  at  the  top  of  the  wind- 
pipe, it  cannot  be  modified  by  its  length  or  size  ;  while 
in  birds,  the  voice  being  formed  at  the  bottom  of  the 
wind-pipe,  it  is  necessarily  modified  by  the  length  and 
size  of  this  part,  and  of  the  opening  at  the  top,  for  it 
must  traverse  all  this  space  before  it  can  come  to  the 
mouth. 

Emily. — And  is  it  found  to  be  the  case  that  those  with 
long  wind-pipes  have  the  lowest  or  gravest  voices,  and 
those  with  short  wind-pipes,  the  highest  or  acutest 


TRACHEA    OF    BIRDS. 


186 


voices  ?     For  the  longer  a  tube  is,  you  know,  in  which 
a  sound  is  uiade,  the  lower  will  be  its  pitch. 

Dr.  B. — The   fact  is  confirmed  satisfactorily  by  ob- 
se.'v   tion,  thnt  in  different  birds,  those  have  the  highest 
voices  which  h  v    the  shortest  wind-pipes,  and  vice  versa. 
In  the  vocal  organs  of  birds,  we  find  some  curious 
forms  of  structure,   which  so  far  as  we  are  acquainted 
with  the  subject,   do  not  seem  to  have  any  particular 
purpose.     Some  of  the  Gallinacea3  order,  among  which 
we  may  mention  the  domestic  cock,  the  pheasant,  some 
liver  birds,   some  of  the  anseres, 
as  the  swan,  and  some  wild  ducks, 
have    large  inflated  pouches  con- 
nected with  the  inferior  larynx,and 
communicating   freely  with  it. — 
Here  is  the  larynx  of  a  wild  duck, 
differing  very  little,  however  from 
that  of  our    domestic    duck.     In 
some   river  birds,   the  wind-pipe 
is  convoluted  or  coiled  round  upon 
itself*     Here  is  a  specimen  of  this 
structure    in   the  wind-pipe  of  a 
crane,  where  its  convolutions  are 
contained  with- 
in the   sternum 
or  breast-bone. 
In  some  other 
species  howev- 
er, it  is  not  en- 
closed   in    the 
sternum.  What 
is    a    little    re- 
markable,   this 
structure  is  fre- 
quently posses- 
sed by  one  sex. 
and  not  the   other,  of  the  same  species.     The  voice  in 
nearly  all  those  birds  whose  wind-pipe  is  convoluted  in 
16* 


186  CRIES. 

this  way,  is  uncommonly  harsh  and  disagreeable,  and 
not  very  intense. 

Emily. — You  say  these  birds  with  convoluted  tracheae 
have  not  intense  voices,  but  the  crane  and  swan  are  large 
birds,  and  we  should  think  they  would  have  intense 
voices. 

Dr.  B. — It  is  found  by  observation  that  the  intensity 
of  the  voice  in  birds,  depends  on  the  strength  of  the 
muscles  connected  with  the  vocal  organs,  and  it  is  not 
true  that  the  strength  of  these  mucles  is  always  propor- 
tioned to  the  size  of  the  bird. 

It  has  been  found  by  Mr.  Hunter,  that  in  singing-birds, 
the  loudest  songsters  have  the  strongest  muscles  connec- 
ted with  their  vocal  organs.  The  English  lark  whose 
voice  is  so  intense  that  it  may  be  heard  after  he  has  risen 
in  the  sky  out  of  sight,  has  the  most  powerful  muscles 
of  all  the  singing-birds. 

Emily. — As  Shelly  beautifully  speaks  of  it — 

Like  a  star  of  heaven 

In  the  broad  day-light, 
Thou  art  unseen,  but  yet  I  hear  thy  shrill  delight. 

Dr.  B. — The  organs  of  voice  in  reptiles  are  much  less 
complicated  in  their  construction  than  in  all  other  animals, 
and  hence  their  voice  consists  of  a  mere  croaking,  his- 
sing sound.  In  the  adder,  viper,  and  the  serpents  in 
general,  we  find  only  a  glottis,  and  of  course,  the  voice 
is  imperfect  in  proportion  to  the  imperfection  of  the  or- 
gan. Serpents  are  not  known  to  utter  any  other  sounds, 
than  mere  hisses,  and  those  only  when  enraged.  The 
tortoises  seem  to  be  unable  to  utter  any  sound  whatever. 

Emily. — The  frogs  have  no  reason  to  complain  that 
nature  has  not  endowed  them  with  vocal  powers  of  no 
contemptible  strength  and  volume. 

Dr.  B. — Having  now  spoken  of  those  "  various  in- 
struments with  which,  animals,  each  playing  his  part, 
perform  the  great  concert  of  nature,"  we  shall  speak 
more  particularly,  to  continue  the  figure,  of  the  music  it- 
-elf.  Man  like  other  animals,  is  capable  of  uttering 


SPEECH    LEARNED    BY    IMITATION.  187 

cries,  by  which  he  expresses  his  most  simple  instinctive 
wants  and  passions. 

Emily. — Foi  this  reason,  the  cry  is  termed  the  nat- 
ural voice,  1  suppose,  being  a  gift  of  nature,  and  com- 
mon to  the  new  born  babe,  as  well  as  to  the  adult  in 
years. 

j}r%  J5. — In  contr, [distinction  to  this,  is  what  is  called 
the  acquired  voice,  including  speech  and  singing.  "Cries 
generally  include  the  most  intense  sounds  that  the  voice 
is  capable  of  forming,  and  are  characterised  by  a  pecu- 
liar tone  which  easily  distinguishes  them  from  all  other 
sounds.  They  establish  important  relations  between 
man  and  his  fellow  creatures.  A  cry  of  joy  imparts 
pleasure,  a  cry  of  grief  excites  pity,  and  the  cry  excited 
by  fear  carries  terror  to  a  distance."  In  whatever  situa- 
tion man  is  found,  he  is  capable  of  uttering  cries.  The 
new  born  infant,  the  decrepit  old  man,  the  deaf  person 
and  the  idiot,  are  all  capable  of  uttering  cries ;  and  we 
must  therefore  consider  this  function  as  essentially  de- 
pending on  organization.  The  social  wants  and  pas- 
sions not  being  inseparably  connected  with  organization, 
have  no  peculiar  cries. 

Man  endowed  with  reason  and  the  sense  of  hearing, 
in  a  state  of  society,  soon  perceives  that  his  fellow  crea- 
tures utter  other  sounds  than  mere  cries,  and  by  imita- 
tion he  is  enabled  to  make  similar  sounds.  This  is  call- 
ed acquired  voice,  and  inasmuch  as  it  is  the  result  of 
hearing,  and  of  an  intellectual  effort,  the  deaf  child,  as 
he  never  hears,  cannot  imitate  the  sounds  of  others  ;  nor 
can  the  ideot,  for  lie  is  incapable  of  establishing  any  re- 
lations between  the  sounds  he  hears,  and  those  he  is  able 
to  produce. 

Emily. — Have  the  deaf  and  dumb  the  organ  of  hear- 
ing only  defective  ?  I  presumed  their  vocal  organs  were 
also  defective. 

Dr.  B. — No — their  vocal  organs  are  perfectly  sound, 
but  remain  forever  in  complete  -inactivity,  because  they 
are  never  stimulated  by  the  wish  of  uttering  sounds. 


188  SPEECH    LEARNED    BY    IMITATION. 

Emily. — I  had  no  idea  that  speech  is  so  exclusively 
a  thing  of  imitation.  A  person  then  who  should  be  se- 
cluded from  all  society  from  infancy,  would  be  destitute 
of  the  power  of  speech. 

Dr.  B. — Not  precisely  so,  neither,  for  the  power  of 
hearing  still  remaining,  he  could  not  help  becoming  ac- 
quainted with  some  kind  of  sounds.  Hence  he  would 
be  capable  of  uttering  articulate  sounds,  though  they 
would  be  obscure  and  unintelligible  to  every  body  else. 
Every  individual  speaks  the  language  that  he  has  learnt 
from  others  ;  in  the  situation  you  refer  to,  he  could 
learn  no  known  language,  but  would  form  one  of  his 
own,  though  it  would  amount  to  nothing  more  than  a 
confused  jumble  of  strange  sounds.  However,  to  re- 
move all  doubt  from  your  mind,  let  me  relate  a  curious 
story  illustrative  ^of  this  doctrine,  which  I  have  on  un- 
doubted authority  : — 

Several  years  ago,  there  lived  in  the  county  of  Wash- 
ington, State  of  Maine,  a  family,  of  which  the  children, 
though  having  the  sense  of  hearing  perfectly,  and  being 
apparently  as  active  and  intelligent  as  other  children, 
could  not  talk.  They  lived  in  a  thinly  inhabited  part 
of  the  country,  and  at  two  or  three  miles'  distance  from 
any  other  family.  The  father  at  length  grew  very 
anxious,  fearing  there  was  a  physical  defect  in  their  vo- 
cal organs,  and  requested1  some  intelligent  gentlemen  in 
a  neighboring  town,  to  examine  the  children,  and  say 
whether  any  thing  could  be  done  for  their  relief.  These 
gentlemen  accordingly  went  and  found  the  children  ac- 
tive, sprightly,  and  able  to  understand  whatever  was 
said  to  them,  as  far  as  ari^  children  could  be  expected 
to,  who  had  lived  in  such  seclusion  from  the  rest  of  the 
world.  The  oldest  one  was  thirteen  years  old  and 
could  pronounce  distinctly  several  common  words  and 
phrases,  as  yes  sir — no  sir — milk — bread — door,  &c. 
and  so  could  the  next  oldest ;  but  they  were  incapable 
of  pronouncing  any  sentence  of  six  words.  What  was 
remarkable,  they  had  a  language  of  their  own  which 


VOICE    IMITATED    BY    MECHANICAL,    MEANS.      J  80 

Consisted  of  signs  and  a  jumble  of  articulate  sounds  not 
belonging  to  any  known  language,  and  by  these  means, 
they  could  easily  carry  on  a  conversation  with  each 
other.  The  true  solution  of  this  strange  affair  soon 
suggested  itself  to  the  gentlemen  present.  They  knew 
that  both  the  parents — very  honest  and  industrious  peo- 
ple— were  remarkable  for  their  taciturnity, — they  never 
spoke  except  when  it  was  absolutely  necessary  to  speak, 
and  then  they  practised  the  most  rigid  economy  in  the 
use  of  words.  It  was  directly  explained  to  their  parents, 
that  the  children  could  not  talk  for  a  very  good  reason 
— they  never  had  an  opportunity  to  learn — they  never 
had  heard  any  body  talk.  The  father  was  therefore 
persuaded  to  remove  with  his  family  to  his  native 
town  in  Massachusetts  where  his  children  would  neces- 
sarily meet  with  other  children,  from  whom  they  might 
learn  to  talk.  This  he  did,  and  in  a  short  time  his 
children  talked  as  well  as  others. 

Emily. — A  curious  story  indeed,  and  with  few  paral- 
lels, I  suspect.  It  reminds  me  of  one,  however,  of  a 
similar  nature,  which  I  have  read  in  some  history  of  the 
Egyptians.  The  king  of  the  Egyptians  ordered  a  couple 
of  young  children  to  be  confined  alone  and  supplied  with 
proper  nourishment,  but  to  hear  the  sound  of  no  human 
voice,  for  the  purpose  of  seeing  what  language  they  would 
use,  and  hence  determining  which  was  the  most  ancient 
nation.  After  a  time,  it  was  found  that  they  frequent- 
ly exclaimed,  bekkos,  a  word  which  it  was  ascertained 
meant  bread  in  the  Phrygian  language;  hence  it  was 
concluded  that  the  Phrygians  were  the  most  ancient  peo- 
ple. The  author  remarked,  that  they  probably  learnt  this 
sound  from  the  goats  which  supplied  them  with  milk. 

Dr.  B. — It  is  hardly  necessary  I  should  remind  you, 
that  articulation  is  performed  not  in  the  larynx,  but  in 
mouth  by  the  aid  of  the  tongue,  teeth  and  lips.  It  is 
peculiar  to  man,  though  imitated  to  a  certain  extent  by 
parrots,  and  some  ingenious  mechanical  inventions, 
a  specimen  of  which  has  been  lately  exhibited  in  this 
country  by  Mr.  Maelzel. 


190  ELEMENTARY    SOUNDS. 

Emily. — You  allude  to  the  little  doll-like  figures  that 
uttered  papa — but  I  did  not  suppose  there  was  any.  thing 
very  wonderful  in  this. 

Dr.  B. — Mechanicians  have  considered  the  imitation 
of  the  human  voice  by  mechanical  contrivances,  as  one 
of  the  most  masterly  efforts  of  art.  M.  Kemperlin  the 
original  inventor  of  the  Automaton  Chess  Player,  suc- 
ceeded in  constructing  a  figure  which  would  utter  a 
continued  sentence,  but  the  manner  in  which  he  obtain- 
ed this  result  is  now  not  known. 

The  elementary  sounds  which  the  vocal  organs  pro- 
duce are  very  few  in  number,  not  more  than  twenty,  and 
some  reduce  them  to  ten.  These  sounds  by  their  vari- 
ous combinations,  make  up  those  compound  sounds  of 
which  every  language  is  formed. 

Emily. — In  the  same  manner,  I  suppose,  that  seven 
notes  in  music  are  made  capable  of  expressing  every 
variety  of  harmony  that  has  been,  or  can  be  made. 

Dr.  B. — In  our  own  language,  the  elementary  sounds 
amount  to  twenty-four,  though  some  of  them  are  but 
slight  modifications  of  others.  The  vowels,  a,  e,  i,  o,  u, 
are  formed  by  the  chink  of  the  glottis  alone  ;  the  gut- 
tural, k,  ch,  q,  g,  h,  are  formed  in  the  throat,  which  is 
assisted  in  some  degree  by  the  chink  of  the  glottis  ;  the 
nasal,  as  m,  n,  are  formed  near  the  nasal  fossae  ;  the 
lingual,  as  /,  r,  chiefly  by  the  tongue  ;  the  labial,  as 
b,p,f,v,  w,  by  the  lips  5  and  dental,  as  c,  t,  z,  d,  by 
the  teeth. 

The  voice  of  speech,  like  the  natural  voice,  consists 
of  sounds  not  easily  appreciated  ;  that  is,  not  easily  re- 
duced to  a  definite  scale,  as  are  the  sounds  of  the  voice 
of  song. 

Emily — But  do  not  the  various  inflections  of  the 
voice  set  down  by  writers  on  elocution,  show  that  some- 
thing of  this  kind  may  be  done  ? 

Dr.  B. — It  is  true,  they  do,  but  in  a  very  imperfect 
way. — Singing,  like  speech,  is  the  effect  of  a  state  of 
society,  and  supposes  the  existence  of  hearing  and  intel- 


MTSICAL    EAR.  191 

ligence.  Of  ail  instruments  which  the  musical  art  em- 
ploys, the  human  larynx  is  indisputably  the  most  perfect. 
It  cannot  have  escaped  your  observation,  that  in  men, 
the  larynx  is  much  more  prominent,  than  in  women  ; 
indeed,  it  is  rarely  conspicuous  in  females,  except  in 
such  as  have  been  wasted  by  disease.  You  may  also 
have  observed  that  the  voice  of  the  adult  male  is  an  oc- 
tave lower,  than  the  voice  of  females  and  boys. 

Emily. — I  have  always  observed  this  difference,  but 
never  thought  of  asking  the  cause  of  it,  purely,  I  believe, 
because  it,  is  so  common  a  fact.  I  suppose  that  the  or- 
gans are  differently  formed,  are  they  not  ? 

Dr.  B. — They  differ  principally  in  their  size — being 
smaller  in  females  than  in  men  ;  of  course,  the  voice  will 
be  a  little  higher,  reasoning  on  mechanical  principles.  The 
extent  or  compass  of  the  human  voice  in  well-formed 
sounds,  seldom  exceeds  ten  notes ;  but  the  compass  of 
the  male  voice  may  be  extended  four  or  five  notes  by 
the  use  of  what  is  called  the  falsetto,  which  resembles 
the  treble  voice. 

Emily. — Voices  not  only  differ  in  pitch  and  intensity, 
but  every  one  has  its  own  peculiar  tone  which  distin- 
guishes it  from  all  others,  so  that  we  remember  a  per- 
son's voice  as  long  as  we  do  his  countenance.  Besides, 
the  voice,  generally  speaking,  is  distinguished  by  other 
characters, — these  are  strong  voices  ;  soft,  harsh,  flexi- 
ble, melodious  voices,  &ic.  Are  all  these  the  result  of 
organization  ? 

Dr.  B. — Undoubtedly,  the  great  diversity  in  pitch, 
tone  and  character  of  the  voice,  results  mainly  from  di- 
versity in  the  structure  of  the  vocal  organs,  though  some 
change  in  this  respect,  may  be  effected  by  education. 

Emily. — The  different  degrees  of  excellence  with 
which  people  sing,  are  also,  I  suppose,  to  be  attributed 
to  the  organization  af  the  vocal  organs. 

Dr.  B. — To  a  certain  extent,  they  are,  but  not  en- 
tirely. The  power  of  singing,  that  is,  of  producing  the 
notes  of  the  musical  scale  correctly  in  various  combina- 


19  VENTRILOQUISM. 

tions,  depends  on  the  accuracy  of  the  ear — the  intellec- 
tual ear,  I  mean,  or,  as  the  phrenologists  would  say,  tlu 
organ  of  time.  The  perception  of  musical  sounds,  evi- 
dently belongs  to  a  distinct  intellectual  faculty,  for  the 
ear  may  be  able  to  distinguish  very  accurately,  common 
sounds,  and  yet  the  individual  be  insensible  to  the  per- 
ception of  musical  sounds. 

Emily. — And  yet  we  hear  it  observed  every  day, 
that  this,  or  that  person  has  no  voice  for  singing. 

Dr.  B. — Such  language  is  incorrect,  for  if  a  person 
can  talk,  he  can  utter  the  notes  of  music,  and  this  is  all 
that  is  required  of  the  voice  in  singing.  A  person's  voice 
maybe  harsh,  weakj  or  unpleasant  in  any  Way,  but  if 
the  tasle  be  good,  the  voice  is  always  capable  of  inton- 
ating correctly  within  certain  limits.  In  good  singers, 
indeed,  the  vocal  organs  exist  in  a  state  of  great  perfec- 
tion, so  that  the  mere  sound  of  their  voice  imparts  a 
pleasurable  sensation  to  the  physical  ear.  But  the  most 
wonderful  perfection  of  the  vocal  organs,  is  probably 
found  in  ventriloquists. 

9  Emily. — I  am  glad  that  you  are  going  to  speak,  be- 
fore we  quit  this  subject,  of  ventriloquism.  Do  explain 
wherein  consists  the  secret  of  this  curious  art.  It  would 
appear  at  first  sight,  that  these  persons  had  some  pecu- 
liarity of  construction  in  their  vocal  organs,  but  I  believe 
this  is  not  the  case.  The  name  ventriloquism,  would 
indicate  that  the  voice  is  formed  in  the  abdomen. 

Dr.  B. — This  name  was  given  to  it  when  a  great 
mistake  prevailed  in  regard  to  its  nature,  and  is  alto- 
gether improper  now.  The  voice  of  the  ventriloquist 
in  fact,  is  formed  in  the  larynx,  as  in  ordinary  speech. 
You  recollect  when  we  were  speaking  of  the  sense  of 
hearing,  it  was  observed,  that  we  easily  learnt  to 
distinguish  the  distance  and  direction  of  sounds  by 
a  certain  peculiarity  of  tone  not  easily  described. 
The  sound  of  a  person's  voice  undergoes  different 
modifications,  according  as  it  is  near  or  at  a  dis- 
tance, comes  from  above  or  below,  from  the  room  or 


VOICE    OF  BIRDS. 


the  open  air,  &:c.  Now  the  ventriloquist  having  the  or- 
gan of  voice  in  great  perfection,  and  having  been  accus- 
tomed for  a  long  time,  to  pay  particular  attention  to  the 
difference  between  these  various  modifications,  becomes 
able  at  last,  to  imitate  them  so  perfectly  as  to  deceive 
the  most  wary.  Thus,  he  knows  very  well  how  a  voice 
sounds  which  comes  from  the  opposite  side  of  the  room, 
and  his  endeavor  is  to  imitate  that  sound.  If  he  succeeds, 
it  will  seem  to  come  from  that  quarter,  though  it  is  indif- 
ferent where  he  may  be  placed.  If  other  delusions  are 
ma'de  use  of,  the  deception  is  still  more  complete.  "In 
one  respect,"  says  Majendie,  "  this  art  is  to  the  ear, 
what  painting  is  to  the  eye." 

Emily.  —  What  wonderful  results  will  not  education 
produce,  with  some  of  our  physical  organs  !  Who,  on 
hearing  the  voice  of  ventriloquism  for  the  first  time, 
would  attribute  it  to  this  cause  ! 

Dr.  B.  —  No  one,  we  may  safely  say,  for  almost  every 
possible  theory  was  started,  before  the  true  one  was  sug- 
gested. But  in  all  this  perhaps  there  is  nothing  more 
strange,  than  the  power  by  which  hunters  imitate  the 
voices  of  animals,  and  thus  decoy  them  to  their  snares. 

We  might  here  conclude  the  subject  of  the  voice,  but 
as  many  interesting  observations  on  the  voice  of  birds 
have  been  recorded,  I  cannot  help  making  you  acquaint- 
ed with  a  few  of  them. 

Emily.  —  Do  by  all  means  —  for  who  that  has  heard 
the  sweet  voices  of  these  little  songsters,  can  find  any 
information  relative  to  them,  tedious  or  uninstructive  ? 

Dr.  B.  —  To  chirp,  is  the  first  sound  which  a  young 
bird  utters,  as  a  cry  for  food,  and  is  different  in  all  nest- 
lings ;  so  that  the  hearer  may  distinguish  of  what  species 
the  bird  is,  though  the  nest  hangs  out  of  sight.  This 
cry  is  very  weak  and  querulous  ;  it  is  dropped  entirely 
as  the  bird  grows  stronger,  nor  is  it  afterwards  mingled 
with  its  song. 

The  call  of  a  bird  is  that  sound  which  the  bird  is  able 
to  make  when  about  a  month  old  ;  it  is  in  most  instances, 


194  ORIGIN    OF    THE    SONGS    OF    BIRDS. 

a  repetition  of  one  and  the  same  note,  is  retained  during 
life,  and  is  generally  common  to  both  male  and  female. 
This  stage  in  the  notes  of  birds,  is  called  recording,  and 
is  the  first  attempt  of  the  nestling  to  sing, — it  may  be 
aptly  compared  to  the  first  attempts  of  the  child  to  talk. 
At  first,  we  are  not  able  to  perceive  the  least  rudiment 
of  the  future  song,  but  as  the  bird  grows  older  and  stron- 
ger, we  see  what  he  is  aiming  at.  When  the  nestling  is 
once  sure  of  his  strain,  he  commonly  raises  his  voice, 
and  sings  out  boldly ;  but  he  hurries  over  those  parts  of 
which  he  is  not  perfect  master,  lowering  his  voice  as  if 
he  could  not  yet  satisfy  himself,  and  did  not  wish  to  be 
heard.  The  young  bird  commonly  continues  to  record 
for  ten  or  eleven  months,  when  he  is  able  to  execute  ev- 
ery part  of  his  song,  which  afterwards  continues  fixed, 
and  is  scarcely  ever  altered.  When  the  bird  is  thus 
perfect  in  his  lesson,  he  is  said  to  sing  his  song  round. 

Emily. — Every  species,  I  believe,  has  its  own  pecu- 
liar song — does  this  difference  of  song  depend  on  a  spe- 
cific difference  in  the  structure  of  the  vocal  organs  ? 

Dr.  B. — It  would  seem  very  rational  to  suppose,  that 
the  physical  organs  being  different,  the  sounds  they  pro- 
duce, would  be  so  of  course.  Yet  it  has  been  said  that 
the  song  of  birds  is  no  more  innate,  than  language  in 
man,  but  depends  on  the  master  under  which  they  are 
bre.f]__SQ  far  at  least  as  their  organs  will  enable  them  to 
imitate  the  sounds  they  hear.  In  proof  of  this  opinion, 
many  experiments  have  been  related,  in  which  birds 
have  been  taken  from  the  nest  while  quite  young,  and  re- 
moved to  those  of  a  different  species.  The  results  were, 
that  the  birds  thus  removed,  had  the  song  of  their  foster 
parents,  and  not  of  their  own  species. 

Emily. — These  experiments  then  are  perfectly  satis- 
factory, I  should  think,  in  proving  the  truth  of  the  opin- 
ion, that  their  songs  are  learnt,  and  not  innate. 

Dr.  B.  — So  it  would  seem,  but  most  unluckily  four  or 
five  years  ago,  (these  experiments  were  performed  in 
the  last  century)  an  intermeddling  naturalist  took  it  into 


ACCURACY    OF    BIRDS*    EAR.  195 

his  head  to  institute  a  series  of  similar  experiments,  and 
lo  !  their  results  were  just  the  reverse.  How  to  recon- 
cile them,  is  more  than  we  know,  so  that  lor  the  present 
we  must  be  content  to  have  no  opinion  on  the  subject. 

Emily. — Verily,  I  think  we  are  like  the  metaphysical 
ass  between  two  bundles  of  hay,  starving  to  death  for  lack 
of  a  sufficient  motive  to  prefer  one  to  the  other. 

Dr.  B.— How  birds  originally  came  by  the  notes 
which  are  now  peculiar  to  each  species,  we  do  not  know  ; 
nor  do  we  know  why  every  nation  has  its  peculiar  lan- 
guage and  music.  The  power  of  singing  belongs  but  to 
few  species  of  birds  and  is  mostly  confined  to  the  males. 
In  their  wild  state  they  do  not  generally  sing  more  than 
two  weeks  in  the  year. 

Emily. — Now  however  agreeable  all  this  singing  may 
be  to  us  who  hear  it,  I  cannot,  for  my  life,  comprehend 
what  important  purpose  in  the  economy  of  birds  them- 
selves, is  answered  by  it. 

Dr.  B. — It  would  puzzle  a  wiser  head  than  mine  to 
enlighten  you  on  this  point.  It  has  been  supposed  that 
the  motive  of  the  male  bird  in  singing,  is  to  amuse  and 
solace  his  partner,  during  the  tedious  process  of  incuba- 
tion. But  surely  this  motive  cannot  induce  birds  kept 
in  cages  to  sing  as  they  do,  nine  or  ten  months  in  the 
year. 

Emily. — How  accurate  to,  is  the  ear  of  singing  birds  1 
They  readily  learn  any  song  from  one  another,  and  learn 
many  of  our  common  tunes  from  the  flute  or  flagelet. 
I  saw  two  or  three  years  ago,  in  Boston,  several  robins 
which  an  old  man  had  taught  to  sing  yankee  doodle  per- 
fectly. The  mocking  bird  will  sing  almost  any  short 
strain  after  hearing  it  once  or  twice,  and  I  have  known  a 
parrot  which  is  not  a  singing  bird,  sing  part  of  a  catch 
with  accuracy.  Instances  of  Canary  and  other  birds 
learning  our  music,  are  very  common. 

Dr.  B. — But  the  accuracy  of  a  birds'  ear  appears 
still  more  remarkable  in  this  fact — that  they  always  sing 
in  the  same  key ;  and  it  is  owing  to  this  that  we  never 


i96  NOTATION  OP  BIRD'S  SONGS. 

hear  a  bird  unable  to  complete  his  strain,  as  we  often  are, 
by  taking  a  pitch  above  or  below  the  compass  of  the 
voice. 

Emily. — Have  there  been  any  attempts  made  to  re- 
duce their  songs  to  our  musical  notation  ?  It  would  be 
quite  pleasant  to  have  the  songs  of  some  birds  written 
out,  and  play  them  OH  the  piano. 

Dr.  B. — Such  attempts  have  been  frequently  made, 
but  in  most  instances  an  insurmountable  difficulty  is  found 
in  the  minuteness  of  their  intervals.  The  smallest  in- 
terval in  common  use  in  music,  you  know  is  the  semi- 
tone, and  although  much  smaller  intervals  are  used  in 
harmony,  they  are  not  easily  appreciated  in  simple  melo- 
dy— probably  on  account  of  our  being  so  accustomed  to 
the  grosser  intervals.  In  some  instances  however,  we 
find  no  difficulty  in  writing  the  notes  of  birds  on  our 
staff.  The  song  of  the  cuckoo,  is  a  well  known  and 
striking  instance  of  this,  in  which  the  interval  of  minor 
third  occurs.  But  our  time  is  too  far  gone,  to  say  any 
more  on  this  subject. 


BONKS- 


197 


CONVERSATION  VIII* 


Locomotive  organs — bones — composition  of  bone —  ossi- 
fication— nutrition  and  reparation  of  bones — -joints — 
skeleton — skeleton  of  the  loiver  animals — adaptation  of 
the  human  skeleton  to  the  erect  position — human  foot 
and  hand.- — The  muscles — attachment  of  the  muscles 
to  the  bones- — action  of  the  muscles,  on  the  principle  of 
the  lever. — Standing — mechanical  contrivances  in  the 
leg  of  birds — walking — leaping running — influ- 
ence of  education  on  the  muscles — gymnastic  exercises. 

Dr.  B. — Having  finished  the  functions  of  the  nervous 
system,  we  come  next  to^those  of  the  locomotive  organs  ; 
those  by  which  we  are  enabled  to  act  upon  foreign  ob- 
jects, and  transport  our  bodies  from  pla^e  to  place  ac- 
cording to  the  suggestions  of  the  will.  The  organs  of 
motion  may  be  divided  into  classes ;  the  active,  and  the 
passive — the  former  composing  the  muscles ;  the  lalter,. 
the  bones.  And  first  let  us  speak  of  the  bones. 

Many  of  the  inferior  animals  have  in  the  interior  of 
their  bodies  and  limbs,  a  certain  series  of  bones  connec- 
ted together  by  a  definite  method  of  arrangement,  which 
so  far  as  it  exists,  is  generally  the  same  in  all.  This 
series  of  bones  is  called  the  skeleton..  It  constitutes  the 
basis  and  support  of  the  soft  parts,  and  gives  to  the  body 
its  general  forms  and  dimensions.  The  substance  of 
which  a  bone  is  composed,  is  of  two  kinds.  That  com* 
posing  the  external  portion  of  the  bone,  is  of  a  hard  con> 
17* 


198 


USE    OF    THE    MARROW. 


pact  texture ;  while  the  centre  is  occupied  by  a  substance 
of  more  soft  and  spongy  nature.  The  proportions  of 
these  two^arts  vary  in  different  bones,  and  in  different 
portions  of  the  same  bone.  Thus,  the  compact  substance 
composes  chiefly  the  shaft  or  body  of  the  bone ;  while 
the  head  and  the  other  extremity  of  the  bone  is  formed 
almost  wholly  of  the  spongy  substance  surrounded  by  a 
thin  covering  of  the  compact.  In  the  centre  of  the  long 
bones,  a  hollow  space  is  left  which  is  filled  by  a  fatty 
substance,  called  tne  marrow. 

Emily. — I  connot  comprehend  what  purpose  is  an- 
swered by  this  spongy  structure,  which  composes  so 
great  a  portion  of  the  bone.  To  me  it  seems  to  increase 
unnecessarily  the  size  and  weight  of  the  bones,  without 
adding  in  the  least  to  their  strength. 

Dr.  B. — You  are  entirely  mistaken, — for  the  very 
effect  of  this  kind  of  structure  is  to  increase  the  strength 
of  the  bone.  If  the  compact  parts  of  the  bone  were  all 
united  together  into  a  solid  piece  without  any  space  in 
the  centre,  the  bones  being  diminished  in  size,  would 
more  easily  yield  to  external  force ;  for  it  is  demonstra- 
ted by  mathematics,  that  the  same  quantity  of  matter  in 
the  form  of  a  hollow  cylinder  is  capable  of  resisting  a 
greater  external  force,  than  in  the  form  of  a  solid  cylin- 
der, the  length  being  the  same  in  both.  Hence,  it  is 
generally  found  that  in  those  parts  of  the  body  where 
strength  is  required  without  much  additional  weight,  the 
bones  have  considerable  spongy  substance  in  their  centre. 

JEmily. — And  the  marrow — what  is  the  use  of  this  ? 
A  store  of  nourishment  laid  up  for  the  use  of  the  bone  ? 

Dr.  B. — It  cannot  be  for  the  nourishment  of  the  bone, 
and  yet  it  is  difficult  to  say  what  its  actual  use  is.  It  has 
been  supposed  to  be  diffused  through  the  substance  of 
the  bone,  and  thus  to  render  them  less  brittle.  It  has  also 
been  conjectured  that  its  use  in  the  animal  economy  is 
the  same  as  that  of  other  animal  oils,  and  that  the  centre 
of  the  bones  being  a  very  convenient  reservoir,  it  was 
placed  here  for  this  reason  simply. 


RICKETS.  199 

Emily. — What  is  the  chemical  composition  of  the 
bones  ?  I  should  imagine  that  strong  materials  were  re- 
quired. 

Dr.  B. — The  bones  are  formed  of  two  kinds  of  sub- 
stance, one  animal,  the  other  earthy.  The  latter  serve 
the  purpose  of  giving  the  necessary  firmness  and  solidity 
to  the  bone  ;  but  this  alone  being  exceedingly  brittle,  a 
certain  portion  of  animal  matter  is  obviously  required, 
to  give  it  flexibility  and  power  of  resistance. 

Emily. — Fray  how  do  you  know  so  exactly  what  are 
the  particular  uses  of  these  two  different  substances.  I 
should  like  to  see  some  little  more  satisfactory  evidence 
of  it,  than  the  mere  assertion  of  the  iact. 

Dr.  B. — -You  have  noticed  no  doubt,  how  brittle,  bones 
are,  that  have  been  burnt  in  the  fire, — now  if  these  be 
analysed,  they  will  be  found  to  have  lost  all  their  animal 
matter.  On  the  other  hand,  here  is  a  bone  which  has 
been  kept  some  time,  in  a  jar  of  diluted  muriatic  acid, 
and  you  see  that  though  quite  a  stout  bone,  I  can  easily 
bend  it  up  double  without  breaking  it. 

Emily. — Well,  that  is  singular  indeed  !  But  you  must 
have  the  kindness  to  explain  it. 

Dr.  B. — The  acid  has  united  chemically  with  the 
earthy  portions  of  the  bones  and  removed  them,  leaving 
behind  only  the  animal  matter,  which  being  very  flexi- 
ble yields  to  the  least  force.  Do  you  see  now,  that 
bones  formed  of  either  of  these  substances  alone  would 
want  either  firmness  or  flexibility  ;  but  that  being  com- 
posed of  both,  they  possess  a  proper  share  of  both,  these 
qualities  ? 

Emily. — Yes — 4  see  perfectly  well  now,  how  both 
strength  and  flexibility  are  obtained  by  the  union  of  these 
different  kinds  of  substance. 

Dr.  B. — You  have  seen  children  perhaps,  effected 
with  the  disease  called  rickets,  when  the  limbs  sink  un- 
der the  weight  of  the  body.  Here,  owing  to  some  de- 
tect of  nutrition,  the  bones  are  not  supplied  with  their 
proper  portion  of  earthy  matter.  The  contrary  takes 


SENSIBILITY    OF    THE    BONES.' 

place  in  old  persons — the  bones  are  furnished  with  too 
little  animal  matter.  Hence,  in  falling,  old  people  are 
more  liable  than  young  persons  to  break  their  bones. 

Emily* — \\hat  are  tiie  earths  found  in  the  composi- 
tion of  bones  ? 

Dr.  B. — If  we  except  a  small  portion  of  two  or  three 
other  salts,  the  earthy  substance  of  the  bones,  is  almost 
entirely  phosphate  of  lime — constituting  about  one  half 
of  the  whole  bone.  This  earthy  salt,  you  know,  is  in- 
soluble in  water,  and  will  bear  a  very  high  temperature 
without  decomposition.  Hence,  as  might  be  supposed, 
bones  are  the  most  durable  of  all  parts  of  an  organized 
body,  and  capable  of  resisting,  for  an  astonishing  length 
of  time,  the  influence  of  external  agents.  Bones  are 
now  found  in  the  earth  by  geologists,  of  animals  that 
must  have  perished  long  before  the  last  revolutions  that 
have  changed  the  surface  of  our  globe.  The  animal 
substance  of  bones  is  probably  cartilage, — at  least  it  very 
nearly  resembles  that  substance — with  a  small  quantity 
of  jelly  and  oil  contained  in  the  spongy  substance. 

Emily. — The  bones  being  one  half  mere  earth,  can- 
not, I  should  suppose  be  very  sensible,  and  yet  we  often 
hear  people  complain  of  pain  in  their  bones. 

Dr.  B. — This  is  probably  an  illusion,  for  bones  in  & 
healthy  state  may  be  sawed,  cut,  scraped,  or  broken 
without  causing  the  least  pain,  and  therefore  it  has  been 
considered  by  some  physiologists,  that  they  possess  na 
nerves. 

Emily. — Is  it  known  that  they  possess  blood-vessels,, 
and  absorbents  ?  Do  they  bleed  when  cut  or  broken  ? 

Dr.  B. — The  latter  fact  is  not  necessary  to  prove  the 
existence  of  blood-vessels.  Though  we  can  see  no 
traces  of  blood-vessels  in  the  bones,  yet  many  observa- 
tions and  experiments,  confirm  us  in  the  belief  beyond 
all  manner  of  doubt,  that  the  bones  are  organized  bodies, 
and  of  course  require  arteries,  veins,  absorbents  and- 
serves. 

Emily.' — I  should  like  to  hear  some  of  these  expert 


FORMATION    OF    BONE.  201 

ments  and  observations,  for  I  really  feel  more  interest  in 
this  account  of  the  bones  than  I  had  anticipated. 

Dr.  B. — Attend  then,  with  all  patience,  to  a  few  re- 
marks on  the  formation,  nutrition,  and  restoration  of 
bone.  We  may  examine  an  animal  in  the  first  periods  of 
existence — the  chick  in  the  egg,  for  instance — and  ob- 
serve the  general  shape  of  the  body  and  the  rudiments  of 
limbs,  but  find  no  traces  whatever  of  bone.  In  their 
place,  we  observe  a  soft,  semi-fluid  substance  contained 
within  a  delicate  membrane.  This,  after  a  time,  as- 
sumes the  consistency  of  cartilage,  transparent,  and  col- 
ourless, but  possessing  the  form  of  the  future  bone.  Next, 
the  vessels  which  before  carried  only  white  fluids,  en- 
large and  give  admittance  to  the  red  particles,  and  the 
first  mark  of  ossification  may  be  considered  this  appear- 
ance of  a  little  artery,  filled  with  red  blood,  pursuing  its 
way  into  the  substance  of  the  cartilage.  Other  arteries 
appear  in  it  from  different  directions,  overtake  the  first, 
and  finally  form  a  net-work  of  minute  vessels.  Here 
bony  matter  is  deposited  from  the  mouths  of  these  ves- 
sels, and  at  length  we  have  a  little  centre  or  nucleus  of 
ossification,  spreading  in  the  form  of  fine  rays,  in  all  di- 
rections. In  this  manner,  arteries  appear  in  other  parts 
of  the  cartilage,  and  form  centres  of  ossification,  which 
spread  and  meet  each  other,  and  thus  the  whole  bone  is 
completed.  In  the  long  boues,  there  aie  several  cen- 
tres of  ossification  ;  the  body  and  each  extremity  re- 
ceive a  set  of  vessels  which  enter  it  by  a  common  trunk; 
and  these  parts  are  each  perfectly  formed  before  they 
are  united  together— indeed,  in  some  of  the  bones,  they 
remain  several  years  after  birth,  before  they  are  united 
by  any  thing  more  than  cartilage. 

Such  is  the  way  in  which  bones  are  always  formed ; 
the  plan  is  first  laid  in  cartilage — an  isolated  mass,  with- 
out holes  or  cavities — and  is  afterwards  moulded  into  its 
proper  forms,  during  the  process  of  ossification.  The 
cartilage,  you  see,  is  not  hardened,  nor  converted  in  any 
way  into  bone,  as  the  older  physiologists  believed,  for 


202  NUTRITION    OF    BONE. 

while  the  bony  matter  is  depositing,  a  process  of  no  less 
importance  is  also  going  forward.  The  cartilage  is  ob- 
sorbed  too,  not  merely  where  the  bony  matter  is  deposit- 
ed, but  so  as  to  leave  the  necessary  cells,  cavities  and 
holes,  which  are  to  exist  in  the  future  bone. 

In  the  union  of  broken  bones,  we  find  a  strong  con- 
firmation of  what  has  been  said  on  the  formation  of  bone. 
When  a  bone  is  fractured,  there  is  soon  poured  out  from 
the  vessels  of  its  divided  extremities,  a  soft,  fluid  matter 
— chiefly  the  coagulating;  portions  of  the  blood ; — this 
gradually  becomes  cartilage,  vessels  containing  red  blood 
appear  in  it,  bony  matter  is  deposited,  and  finally  a  ring 
of  bone  completely  surrounds  the  broken  extremities, 
and  cements  them  together  more  firmly  than  before  the 
fracture.  It  is  not  necessary  that  the  ends  of  the  bones 
should  be  placed  in  direct  apposition,  that  union  may  be 
produced.  Cases  frequently  occur,  where,  by  bad  man- 
agement on  the  part  of  the  surgeon,  the  broken  ends 
slip  by  each  other,  and  are  not  restored  to  their  proper 
position.  Here  they  are  connected  by  a  bridge  of  bone, 
which  is  made  between  the  overlapping  extremities,  unit- 
ing them  firmly  to  each  other. 

Emily. — What  a  curious  and  admirable  system  of 
means  truly,  does  this  account  of  the  formation  of  bone 
unfold  1 

Dr.  B. — The  wonder  does  not  cease  here,  for  the 
process  of  the  preservation  and  nutrition  of  bone  is 
equally  curious  with  that  ofits  formation. 

Emily. — What  is  the  necessity  of  nutrition  ?  When 
once  formed,  will  not  a  bone  continue  for  life  ? 

Dr.  B. — Certainly  not ;  you  forget  that  bones  must 
grow  with  the  growth,  and  strengthen  with  the  strength 
of  the  body  ;  that  they  are  always  composed  in  part  of 
living  matter,  and  consequently  subject  to  continual 
change.  As  in  the  other  parts,  so  in  the  bones,  each 
particle  after  a  time  becomes  unfit  for  the  purposes  for 
which  it  was  originally  deposited,  is  taken  away,  and 
new  ones  supply  their  places.  The  fact  of  this  constant 


CLASSIFICATION    OF    THE    BONES.  203 

change  and  renovation  is  tested  by  experiment,  and  the 
rapidity  with  which  it  takes  place,  is  almost  incredible. 
It  has  been  found  by  examination,  that  when  animals  are 
fed  on  madder,  it  penetrates  into  the  bones  and  tinges 
them  with  its  colour.  In  twenty-four  hours,  the  bones  are 
tinged,  and  in  two  or  three  days,  the  colour  is  much  deep- 
ened ;  but  if  it  be  discontinued  for  a  few  days,  the  red 
colour  will  be  found  to  have  entirely  disappeared.  A 
striking  proof  of  the  rapidity  with  which  deposition  and 
absorption  is  carried  on  in  these  parts. 

Emily.— Are  the  bones  enclosed  in  any  sheath,  or 
investing  membrane  ?  I  should  presume  they  would 
not  lie  in  direct  contact  with  the  other  parts. 

Dr.  B. — They  are  all  invested  by  a  thin  fibrous 
membrane,  called  the  periosteum,  which  by  means  of 
its  numerous  vessels,  gives  nourishment  to  the  external 
portions  of  the  bone.  An  injury  therefore,  which  de- 
prives any  part  of  the  bone  of  its  periosteum,  causes 
the  death  of  those  parts ;  they  become  detached  for  want 
of  nourishment,  and  their  place  is  supplied  by  new  ones 
formed  from  the  parts  immediately  beneath  them.  The 
internal  cavity  of  the  bone  is  also  provided  with  its  proper 
membranes  which  in  the  same  way  transmit  the  vessels 
that  nourish  the  adjacent  parts  of  the  bone.  If  now  you 
fully  understand  this  account  of  the  formation  and  nutri- 
tion _of  bone,  we  will  proceed  to  the  next  division  of  our 
subject. 

Emily. — Thus  far,  I  believe,  I  have  a  clear  idea  of 
the  processes  you  have  described,  and  they  are  surely, 
not  the  least  wonderful  in  the  system  of  the  animal  econ- 
omy. 

Dr.  B. — The  bones  in  the  human  body  amount  in  num- 
ber to  about  two  hundred  and  sixty,  and  exhibit  a  great 
variety  of  size  and  figure.  They  are  nevertheless  divi- 
ded into  three  classes ;  the  long,  short,  and  flat  bones. 
The  short  bones  are  found  in  those  parts  whose  motions 
are  confined,  but  complicated,  as  in  the  hand  and  foot. 
They  present  considerable  extent  of  surface,  with  but 


204  CONSTRUCTION    OF    THE    JOINTS 

little  weight,  for  they  are  spongy  in  their  texture.  The 
flat  bones  are  used  to  form  the  walls  of  cavities,  as  the 
skull.  The  long  bones  are  found  in  the  limbs,  and 
are  entirely  employed  in  locomotion. 

Emily. — How  are  bones  connected  together  at  the 
joints,  so  as  to  give  them  the  wonderful  strength,  as  well 
as  facility  of  motion  which  they  enjoy  ?  If  I  am  not 
deceived,  I  suspect  there  is  much  that  is  exceedingly 
curious  in  the  construction  of  these  parts. 

Dr.  B. — Yes — the  structure  and  use  of  the  joints  do 
present  us  some  very  interesting  facts.  They  are  distin- 
guished into  those  that  are  moveable,  and  those  that  are 
immoveable.  A  specimen  of  the  latter,  we  have  in  the 
teeth  and  the  head  ;  but  it  is  the  former  kind  that  we 
wish  more  particularly  to  examine.  Physiologists  have 
pointed  out  two  kinds  of  the  moveable  joint ;  the  ball  and 
socket  joint,  and  the  hinge.  Of  the  former  we  have  a 
specimen  in  the  hip-joint.  The  head  of  the  bone  pre- 
sents a  large  round  surface,  which  is  received  into  a  deep 
cup-like  socket  in  the  hip-bone,  in  which  it  plays  with 
an  easy  motion  in  all  directions.  In  the  elbow  is  an 
instance  of  the  hinge-joint.  The  fore-arm  bends  for- 
ward on  the  arm,  but  in  its  motion  backward,  it  is  stop- 
ped when  on  a  line  with  the  arm,  by  a  process  of  bone 
which  juts  out  from  its  extremity  and  comes  in  contact 
with  the  other  bone. 

In  the  construction  of  the  joints,  every  thing  shows 
the  regard  that  has  been  paid  to  the  security  and  easy 
motion  of  the  parts  thus  connected  together.  The  ends 
of  the  bones  are,  in  the  first  place,  surrounded  by  a  thin 
coating  of  firm  ahd  elastic  cartilage. 

Emily. — I  do  not  see  how  this  can  produce  an  easier 
motion,  than  if  the  ends  of  the  bones  were  naked  and 
perfectly  smooth.  Besides,  cartilage  being  a  substance 
less  hard  than  bone,  would  certainly  wear  out  sooner. 

Dr.  B. — But  though  sooner  exhausted,  it  is  at  the 
same  time,  more  speedily  repaired,  than  bone.  Provi- 
sion for  preventing  the  effects  of  friction,  can  be  more 
easily  provided  also,  in  case  of  cartilages  than  bones. 


THE  SKULL. 


205 


JSmily. — Pray,  what  may  these  provisions  be  ?  I  never 
was  aware  of  the  existence  of  any  other  provision,  than 
the  mere  vitality  of  the  parts. 

£>r.  /?.— -In  all  the  moveable  joints,  we  find  a  mem- 
brane furnished  with  little  glands,  which  pour  out  a  soft 
and  viscid  fluid  ;  this  lubricates  the  joint,  and  by  thus  keep- 
ing it  constantly  oiled,  as  it  were,  obviates  the  injurious 
effects  of  friction.  This  fluid  is  called  the  synovia,  and 
is  poured  out  in  increased  quantities,  when  the  joint  is  in 
use  ;  it  seems  as  if  motion  was  the  proper  stimulus  of  its 
secretion.  When,  however,  motion  is  continued  too  long, 
the  synovial  glands  are  stimulated  beyond  measure,  a 
soreness  is  felt,  and  an  irritation  is  thus  created  in  the 
joint,  which  may  proceed  to  inflammation,  and  serious 
consequences  ensue.  This  effect  may  also  be  produced 
by  very  different  causes,  that  is,  not  a  sufficient  quantity 
of  motion  to  occasion  the  flow  of  the  synovial  fluid. 

Emily. — You  have  not  yet  mentioned  by  what  means 
they  are  connected  at  the  joints  so  strongly  and  securely. 
Dr.  B. — This  is  done  by  means  of  very  thick  strong 
ligaments  which  go  from  the  extremities  of  the  bones  in 
various  directions,  keeping  them  in  their  respective  situ- 
ations, and  limiting  their  movements  on  each  other.  In 
the  hip  joint  a  very  broad  ligament — the  thickest  and 
strongest  in  the  whole  body — completely  surrounds  the 

whole  joint,  forming  a 
sort  of  bag  in  which  the 
bone  moves  with  perfect 
freedom. 

Thus  connected  to- 
gether, the  bones  form 
what  we  have  already 
termed  the  bony  skele- 
ton. At  the  summit  we 
observed  the  globular 
bony  box,  called  the 
skull,  composed  of  sev- 
eral flat  bones  united  by 
18 


206 


THORAX. 


means  of  the  little  processes  which  project  from  the 
edges  of  each  bone  in  a  saw-like  manner,  and  inter- 
lock with  one  another — a  sort  of  union  styled  in  carpen- 
try dove-tailing.  Just  below  the  skull  and  in  front  of  the 
spinal  column,  we  observe  the  bony  cage  formed  by  the 
ribs  and  breast  bone,  containing  the  organs  of  the  chest. 
Terminating  the  spine,  we  find  the  pelvis  a  hollow,  basin 
like  cavity  formed  by  three  large  and  broad  bones.  To 
the  chest  are  attached  the  upper  extremities,  and  to  the 
pelvis,  are  attached  the  lower  extremities.  On  the  up- 
per and  posterior  side  of  the  chest,  and  bound  down  by 
the  powerful  muscles  of  the  back,  is  a  broad  flat  bone 
terminating  above  in  a  short  process  with  an  articulating 
surface,  and  is  called  the  scapula  or  shoulder  blade. 
S  P 


SP 

C.     collar  bone. 
S.    shoulder  blade. 
JR.  R.    ribs. 
S.  T.    breastbone. 
C.  A.    cartilages. 
S.  P.  Spine, 


POSITION    OP    THE    SKULL    ON    THE    SPINE.       207 

To  this  is  attached  the  round  head  of  the  shoulder  bone. 
To  prevent  this  from  falling  forward,  the  collar  bone 
runs  from  the  sternum  to  the  point  of  the  shoulder  on  both 
sides,  and  thus  separates  the  shoulders  and  keeps  them 
securely  in  their  position.  This  completes  the  whole 
skeleton. 

Emily. — I  think  you  remarked  when  entering  on  the 
subject  of  the  bones,  that  many  of  the  inferior  animals 
possess  a  skeleton,  though  it  is  different  in  some  respects 
from  that  of  man.  Wherein  does  this  difference  con- 
sist ? 

Dr.  B. — Chiefly  in  the  want  of  certain  parts,  for  the 
only  ones  which  they  all  have  in  common,  are  the  skull 
and  spinal  column.  The  whales  and  porpoises  have  no 
lower  extremities;  and. in  the  snakes  and  fishes,  we  find 
neither  upper  nor  lower  extremities ;  neither  thorax,  nor 
pelvis.  The  higher  order  of  quadrupeds,  such  as  the 
apes  and  monkeys,  possess  a  skeleton  which  in  the  gen- 
eral arrangement  of  its  parts,  very  nearly  resembles 
man's ;  but  there  are  still  some  very  important  charac- 
ters in  the  latter,  which  clearly  distinguish  it  from  all 
others. 

In  the  first  place,  we  can  see  throughout  its  whole  con- 
formation a  constant  adherence  to  that  plan  of  construc- 
tion and  disposition  of  the  parts,  which  is  best  adapted  to 
the  erect  stature.  The  position  of  the  head  on  the 
spine  affords  a  strong  proof,  of  how  the  principle  of  the 
erect  position  predominates  through  the  whole  structure. 
The  human  skull  is  connected  with  the  spine  nearly  in 
the  centre  of  its  base,  and  is  slightly  inclined  to  prepon- 
derate forward,  yet  it  is  so  nearly  balanced,  that  but  little 
muscular  exertion  is  necessary  to  keep  it  in  equilibrium. 
In  all  other  animals  on  the  contrary,  the  skull  is  connec- 
ted with  the  spine,  at  its  back  part ;  it  projects  very  little 
behind,  almost  the  whole  base  being  in  front  of  the  spine. 
Now,  this  arrangement  requires  for  the  support  and  mo- 
tions of  the  head,  a  large  mass  of  muscles  on  the  back 
of  the  neck,  and  particularly  a  powerful  ligament,  the 
rudiments  of  which  only  are  found  in  man, 


-208  THE    HUMAN    STERNUM. 

Emily. — I  am  conscious  of  this  peculiarity  in  the  po- 
sition of  the  head  in  some  brute  animals,  such  as  the 
horse,  ox,  sheep,  &c.,  but  I  never  observed  any  differ- 
ence  in  this  respect  between  the  monkeys  and  man. 

Dr.  B. — Nevertheless,  in  the  most  perfect  of  the 
ape  kind — those  that  most  nearly  resemble  man  in  the 
point  of  structure — the  space  occupied  by  the  base  of  the 
skull  in  front  of  the  spine,  is  twice  that  behind. 

Emily. — After  all,  I  do  not  clearly  understand  how 
this  arrangement  indicates  the  erect  position  of  man. 

Dr.  B. — Why,  if  he  should  attempt  to  go  about  on 
all  fours,  the  very  few  and  small  muscles  of  the  neck 
would  be  utterly  incapable  of  supporting  the  head,  and  it 
would  inevitably  fall  forward. 

Emily. — This  seems  satisfactory  enough,  but  have 
not  some  philosophers  imagined  that  man  in  a  state  of 
nature,  as  they  call  it,  did  actually  go  on  all  fours,  but 
had  learnt  to  assume  the  erect  position  on  account  of  its 
greater  convenience  ? 

Dr.  B. — True,  there  have  been  men  who  would  de- 
grade our  noble  species  to  a  level  with  the  brutes,  in  its 
origin,  but  few  will  be  found,  I  suspect,  at  the  present 
day,  to  advocate  their  notions.  The  construction  of  the 
human  thorax,  shows  also,  how  thoroughly  this  reference 
to  the  erect  position  has  been  kept  constantly  in  view. 
In  all  other  animals,  its  greatest  diameter  is  from  be- 
fore backwards,  but  in  man  alone,  it  is  flattened  anter- 
iorly ;  its  greatest  diameter  being  from  side  to  side. 
The  tendency  of  this  arrangement  you  will  readily  per- 
ceive. 

Emily. — If  it  extended  to  the  front,  rather  than  to 
the  sides,  its  tendency  to  fall  forward  would  evidently  be 
greater,  but  the  necessary  room  being  obtained  by  ex- 
tending it  at  the  sides,  the  preponderance  forward  is 
greatly  diminished.  Am  I  right  ? 

Dr.  B. — Yes ;  it  likewise  gives  greater  breadth  to  the 
shoulders,  and  consequently  more  extensive  motions  to 
the  arms.  The  human  breast-bone  also  is  remarkably 


THE    HUMAN    FdOT. 


short,  whereby  a  large  space  is  left  between  the  chest 
and  pelvis  unprovided  with  any  bony  support.  The 
weight  of  the  internal  organs  being  in  a  downward  and 
not  in  a  forward  direction,  the  muscular  walls  of  the  ab- 
domen are  sufficiently  strong  to  receive  their  pressure. 

Emily.  —  Which  would  not  be  the  case,  I  presume, 
were  the  natural  position  of  man  on  all  fours  ;  then,  some- 
thing stronger  would  be  required  to  support  the  down- 
ward pressure  of  the  organs,  than  mere  skin  and  muscles- 
Quite  a  forcible  argument  this,  in  favor  of  the  naturally 
erect  position  of  man. 

Dr.  B.  —  In  brutes,  the  breast-bone  is  long  and  nar- 
row, and  the  ribs  extend  far  down  upon  the  spine. 
They  are  often  more  numerous  than  in  man.  In  the 
hyaena,  there  are  32  ;  in  the  horse,  36  ;  in  the  sloth,  46  ; 
while  in  man  there  are  but  24.  Their  chest  is  com- 
pressed laterally,  and  is  narrow  and  keel-shaped  in  front. 

Emily.  —  This  arrangement,  by  bringing  the  fore  feet 
nearer  each  other,  so  that  they  stand  perpendicularly 
under  the  trunk,  will  contribute  to  the  firmness  and  fa- 
cility with  which  this  part  of  the  body  is  supported. 

Dr.  B.  —  Passing  over  several  other  peculiarities  in 
the  structure  of  the  pelvis  and  inferior  extremities,  lei. 
us  look  at  the  foot. 

Emily.  —  Here  must  be  some  important  peculiarities, 
for  no  animal  in  the  world,  that  I  know  of,  has  a  foot  in 
the  least  resembling  man's. 

Dr.  B.  —  The  human  foot,  to  which  is  finally  trans-* 
mitted  the  weight  of  the  whole  body,  is  larger,  broader, 
stronger  and  more  solid  in  proportion  to  the  body,  than 
that  of  any  other  creature.  It  is  formed  by  numerous 
small  bones,  which  being  connected  together  by  means 
of  cartilages,  are  endowed  with  great  firmness  and  elas- 
ticity. The  general  form  of  the  foot  is  that  of  an  arch 
resting  on  its  two  extremities,  the  heel  and  toes.  No 
animal,  besides  man,  rests  the  foot  on  the  heel. 

Emily.  —  But,  what  great  object  is  answered  by  this 
18* 


210  THE    HUMAN    HCE1L. 

difference  in  the  structure  of  the  foot  ?  I  really  do  noi 
observe  any  as  yet. 

Dr.  B. — Consider  one  moment,  and  you  must  see 
how  beautifully  this  arrangement  conduces  to  facility  and 
security  in  walking.  In  setting  down  the  foot  in  walking, 
the  heel  first  touches  the  ground,  but  being  a  little  in  the 
rear  of  the  leg,  does  not  receive  the  direct  weight  of  the 
body. 

Emily. — And  thereby  prevents  a  painful  jar,  which 
would  unavoidably  take  place,  were  the  heel  placed  per- 
pendicularly to  the  leg,  or  directly  under  instead  of  a 
little  behind  it. 

Dr.  B. — Excellent — you  comprehend  the  tendency 
of  these  mechanical  provisions,  as  if  it  were  no  new  sub- 
ject. But  it  is  hardly  possible  that  any  one  who  has 
ever  enjoyed  that  exhilerating  exercise,  dancing,  should 
not  be  struck  with  that  admirable  mechanism  which 
gives  such  grace  and  facility  to  the  movements  of  the 
foot.  The  heel  having  now  touched  the  ground,  the 
weight  of  the  body  falling  a  little  before,  carries  down 
the  rest  of  the  foot  by  a  gradual  and  steady  motion. 
The  heel  and  toes  now  both  touching  the  ground,  some 
force  is  expended  in  spreading  out  and  separating  to 
their  fullest  extent,  the  pieces  of  this  elastic  arch. 

The  human  heel,  by  its  great  size  and  backward  pro- 
jection, has  the  advantage  of  affording  a  large  space  for 
the  attachment  of  the  muscles,  by  which  it  is  raised  in 
progression.  Where  it  rests  on  the  ground,  it  is  covered 
by  nothing  but  skin  and  cellular  tissue,  whereas  in  the 
brutes,  various  muscles  and  tendons  pass  over  the  heel, 
in  their  course  to  the  sole  of  the  foot. 

Emily. — This  must  effectually  prevent  them  from 
walking  like  man,  since  the  muscles  would  be  compressed 
and  prevented  from  action.  But  is  it  so  in  the  apes 
also  ?  The  orang-ulang,  you  know,  is  said  to  walk  like 
man. 

Dr.  B. — They  are  taught  to  walk  sometimes,  but  it 
is  always  with  feeble  and  tottering  steps.  Their  foot  is 


THE    HUMAN    HAND.  2U 

constructed  like  that  of  other  brutes,  and  they  are 
equally  destitute  of  the  other  conditions  of  the  erect 
stature. 

The  office  of  the  lower  limbs  in  the  support  and  pro- 
gression of  the  body,  is  also  indicated  by  their  superior 
length  and  strength.  Their  length  is  equal  to  that  of 
the  head  and  trunk  together,  and  when  compared  with 
those  of  the  orang-utang,  the  latter  appear  remarkably 
slim  and  feeble. 

Emily. — I  hope  you  are  not  going  to  pass  over  what 
is  after  all  the  most  striking  peculiarity  in  the  human 
skeleton,  the  hand. 

Dr.  B.-~ That  would  be  a  sin  of  omission  indeed,  to 
forget  that  member  which  Aristotle  emphatically  denom- 
inates "  the  organ  of  all  organs."  The  Stagyrite  has 
also  said  that  man  alone,  has  hands  really  deserving  the 
name.  This  superiority  arises  chiefly  from  the  size 
and  strength  of  the  thumbs,  which,  by  being  brought  in 
opposition  to  the  fingers,  enables  them  to  grasp  spherical 
bodies,  and  take  a  firm  hold  on  whatever  they  seize.  It 
is  indispensable  in  all  the  mechanical  offices  of  life, 
which  without  it,  could  not  be  exercised  at  all.  A 
French  philosopher,  struck  with  the  superiority  which 
the  hand  gives  him  over  other  animals,  has  written  a 
book  to  prove,  that  man  is  the  wisest  of  all  animals,  be- 
cause he  has  hands. 

Emily. — Wherein  does  the  hand  of  man  differ  from 
that  of  the  monkeys  ?  They  seem  to  handle  objects 
with  as  much  facility,  and  grasp  them  as  firmly  as  man. 
True,  they  are  not  quite  so  well  shaped  and  graceful. 

Dr.  B. — When  closely  examined,  it  will  be  found 
that  these  organs  are  far  less  perfect  than  man's.  In  the 
first  place,  the  thumb,  which  we  said  was  the  most  dis- 
tinguishing member  of  the  human  hand,  is  slender  and 
weak ;  the  other  fingers  are  also  slender  and  long.  Se- 
condly, they  have  no  separate  muscle  to  bend  the  thumb, 
as  man  has,  but  it  is  bent  by  the  same  muscle  that  bends 
the  fingers. 


THE    TENDONS. 

Emily.— And  for  this  reason  they  are  incapable  of 
those  actions  where  the  motion  of  the  thumbs  is  combin- 
ed with  that  of  the  fore  and  middle  fingers,  and  thus  de- 
barred from  performing  those  delicate  operations  that 
are  required  in  works  of  human  art. 

Dr.  B. — This  finishes  our  account  of  the  passive  class 
of  organs,  engaged  in  locomotion. 

Emily. — Next  then  we  come  to  the  active  class,  or  the 
muscles,  which  operate  on  and  set  the  former  in  motion* 
You  said  in  our  first  conversation,  that  they  are  the  mas- 
ses of  red-coloured  flesh,  which  we  see  in  the  shoulder 
of  mutton,  and  are  composed  of  delicate  fibres  running 
parallel  to  one  another  and  in  the  direction  of  the  length 
of  the  muscle. 

Dr.  B. — I  am  glad  your  memory  is  so  faithful ;  for 
the  subjects  we  are  considering,  are  so  connected  to- 
gether, that  if  we  forget  one  part,  we  lose  a  clue  to  all 
the  rest.  The  middle  portion  of  a  muscle  is  always  its 
largest  part ;  then  it  goes  on  diminishing  in  size  towards 
each  extremity,  when  it  terminates  in  what  are  called 
its  tendons.  These  are  of  a  white  shining  appearance, 
beautifully  contrasting  with  the  red  fleshy  mass  cf  mus- 
cle, and  are  formed  of  exceedingly  strong,  but  small 
fibres,  very  intimately  connected  together,  by  a  sort  of 
interlacing  similar  to  what  the  sailors  call  splicing.  They 
are  thus  made  the  most  powerful  texture  in  the  whole 
body,  and  this  joined  with  their  little  bulk,  gives  them 
every  advantage,  without  compromising  the  beauty  or 
convenience  of  the  parts  into  which  they  are  inserted. 

Emily. — The  body  would  indeed  have  been  awkward 
and  full  of  inequalities,  had  the  muscles  terminated  in 
large,  fleshy  extremities. 

Dr.  B. — Now,  several  tendons  may  be  inserted  to- 
gether in  an  extremely  small  spacej  without  producing 
deformity  or  irregularity. 

Emily. — But  into  what  are  the  muscles  inserted? 
Are  they  not  free  and  unattached  ? 

Dr.  B. — Certainly  not ;  liow  then  could  they  have. 


INSERTION    OF  THE    MUSCLES.  213 

acted  on  the  bones  ?  Every  muscle  is  attached  by  its 
extremities,  generally  to  the  bones,  though  in  a  few  in- 
stances one  of  the  .points  of  attachment  may  be  a  soft 
part.  They  are  supplied  with  arteries,  veins  and  nerves 
in  greater  abundance,  than  any  other  organs.  The 
thumb  receives  more  nerves,  than  is  sent  to  the  whole 
liver.  They  are  fixed  to  the  skeleton,  lying  in  succes- 
sive layers  over  one  another,  though  slightly  separated 
by  cellular  tissue,  filling  up  the  general  outline  of  the 
body,  and  giving  distinctness  and  character  to  its  forms. 

Emily. — Those  are  muscles  swelling  under  the  skin, 
in  the  motion  of  the  arms  or  feet,  are  they  not  ?  I  have 
often  observed  them  very  prominent  in  paintings  and 
statues. 

Dr.  B. — More  so  probably,  than  you  ever  did  in  the 
human  figure.  It  is  an  exaggeration  which  the  Italian 
masters  delighted  in,  and  the  moderns  servilely  copy  it 
from  them. 

The  muscles  are  the  grand  organs  of  locomotion, 
moving  the  body  from  place  to  place,  and  giving  us 
power  to  execute  the  most  delicate  operations.  This 
effect  they  produce  by  virtue  of  their  contractile  power, 
of  which  we  have  already  spoken.  The  contraction  of 
a  muscle  by  shortening  the  distance  between  its  two  ex- 
tremities, must  of  course  approximate  the  parts  to  which 
they  are  attached. 

Emily. — You  observed  just  now,  Dr.  B.,  that  the 
muscles  are  attached  to  the  bones,  and  hence  I  cannot 
possibly  conceive  how  this  approximation  can  be  effected. 
For  if  a  muscle  lie  along  on  a  bone  through  its  whole 
length,  with  its  extremities  fixed  in  the  extremities  of  the 
bones,  how  in  the  name  of  common  sense,  can  these  two 
ends  of  the  bone  be  brought  nearer  together,  without 
bending  or  breaking  the  bone. 

Dr.  B. — I  perceive  you  have  one  very  important  fact 
yet  to  learn  about  the  relative  situation  of  the  bones  and 
muscles,  for  they  are  never  inserted  in  the  manner  you 
supposed.  Recollect  that  both  extremities  of  the  mus- 


214 


ACTION    OF    THE    MUSCLES. 


cle  are  not  attached  to  the  same  bone,  but  to  different 
bones.  Of  course,  the  approximation  must  be  effected 
by  the  intervention  of  a  joint,  the  bones  turning  upon 
each  other  as  upon  a  hinge. 

Emily. — Then  the  bones  may  represent  so  many 
levers ;  the  parts  with  which  they  are  connected,  the 
weight  to  be  raised  ;  the  muscle,  the  power  which  acts 
on  the  lever ;  and  the  joint  will  represent  the  fulcrum. 
Why,  I  had  no  idea  before,  that  the  movements  of  the 
body  are  produced  by  forces  acting  so  strictly  on  me- 
chanical principles.  But  levers,  you  know,  are  of  sev- 
eral kinds ;  on  which  of  these  do  the  muscles  act? 

Dr.  B.—A\\  the  three 
different  kinds  of  levers  are 
used  in  the  body,  but  the 
most  common,  is  that  ol  the 
third  kind. 

Emily. — This  is  where 
the  power  is  between  the 
weight  and  the  fulcrum. 
Why,  this  is  the  most  disad- 
vantageous of  them  all. 

Dr.  B.— -That  indeed  ; 
but  though  it  requires  a  grea- 
ter quantity  of  motion,  yet 
this  disadvantage  is  amply 
compensated  for,  by  greater 
convenience, — in  the  con- 
struction of  the  body, every 
consideration  has  been  sac- 
rificed to  convenience.  As 
an  instance  of  the  manner 
in  which  motion  is  produc- 
ed by  muscular  action,  here 
is  a  figure  of  the  bones  of 
the  arm  with  one  of  the 
muscles.  Now  you  see 
how  the  muscle  shortening 


ACTION  OF  THE  MUSCLES.          215 

itself  must  inevitably  bring  the  bones  nearer  together,  or 
in  other  words,  raise  the  arm. 

Emily. — But  only  observe  what  a  great  loss  of  power 
there  is,  in  consequence  of  the  tendon  being  inserted  so 
near  the  joint.  How  much  easier  the  fore  arm  would 
be  raised,  if  the  muscles  were  inserted  nearer  the  hand. 

Dr.  B. — And  most  certainly  it  would  have  been  so, 
had  the  least  possible  expenditure  of  power  been  requi- 
red ;  but  what  is  the  loss  of  this  little  power  to  Him  who 
is  the  Source  of  all  power  ?  An  advantage  is  gained 
by  this  arrangement  which  is  absolutely  necessary,  and 
which  could  have  been  obtained  in  no  other  way — this 
disadvantageous  use  of  power  is  repaid  by  greater  ve- 
locity in  the  motion  which  it  produces. 

Emily. — True ;  I  perceive  now  that  had  the  tendon 
been  inserted  into  the  bone  near  the  wrist,  the  hand 
would  have  been  raised  much  more  slowly. 

Dr.  B. — And  of  course  it  would  have  been  rendered 
almost  useless,  since  of  all  parts  of  the  body,  this  re- 
quires great  rapidity  in  its  motions.  Now,  you  see  a 
very  slight  contraction  of  the  muscle,  (and  the  less  it  is, 
the  quicker  it  is  performed)  is  sufficient  to  raise  the 
hand  even  up  to  the  shoulder,  though  the  part  to  which 
the  muscle  is  attached  is  moved  through  a  very  short 
space. 

Emily. — Another  objection  to  the  muscle  being  in- 
serted into  the  wrist  has  just  struck  me,  which  I  did  not 
observe  before.  When  the  fore  arm  is  bent,  the  mus- 
cle would  rise  up  at  the  bend  of  the  arm,  and  destroy 
every  thing  like  beauty  or  convenience. 

Dr.  B. — This  shows  forcibly,  how  in  the  mechanical 
construction  of  the  body,  every  arrangement  conduces 
to  beauty,  as  well  as  utility.  In  every  instance  where 
there  is  a  loss  of  muscular  power,  we  may  be  sure  that 
it  is  for  some  object  which  could  have  been  obtained  so 
well  in  no  other  way.  It  is  strikingly  exhibited  where 
the  loss  of  power  arises  from  the  obliquity  of  the  muscles. 
For  instance,  two  bones  are  required  to  be  brought  to- 


216 


ACTION    OF    THE  MUSCLES. 


wards  each  other  by  muscular  power.  If  now,  the  mus- 
cle pass  straight  between  them,  this  can  be  effected  only 
to  a. short  distance — say  one  third,  the  muscle  shorten- 
ing itself  one  third  during  its  contraction. 

Emily. — But  if  the  muscle  pass  from  one  bone  to 
the  other  obliquely,  it  may  shorten  itself  no  more,  and 
yet  bring  them  even  twice  as  near.  What  a  simple  con- 
trivance !  but  one  which  I  never  should  have  imagined. 

Dr.  B.-r-lt  is  admirably  witnessed  in  the  ribs,  which, 
during  respiration,  are  constantly  approaching  and  re- 
ceding from  each  other.  In  the  following  figure,  letters 


R.  R.  represent  the  two  ribs.  If  the  fibres  of  the  mus- 
cle by  which  they  are  to  be  approximated,  run  straight 
forward  across  perpendicular  to  the  bones,  they  will 
move  through  only  one  third  of  the  space  between 
them,  supposing  the  muscle  shortens  itself  only  one  third 
during  its  contraction.  But  taking  an  oblique  direction, 
as  represented  in  O,  they  may  contract  but  one  third  of 
their  length,  and  bring  the  ribs  together. 

Another  instance  too,  where  beauty  and  utility  are 
both  obtained  by  a  sacrifice  of  power,  may  be  seen  in 
the  arrangement  of  the  tendons  that  move  the  toes  and 
fingers.  Instead  of  passing  in  a  straight  line  from  the 
arm  to  the  hand,  which  would  have  been  exceedingly 
clumsy,  they  are  bound  down  at  the  wrist  by  a  fibrous 
band,  under  which  they  move  with  perfect  ease,  as  you 
may  see  in  this  next  cut.  In  this  way,  though  greater 
force  is  required,  yet  greater  velocity  is  obtained. 


MUSCULAR    ACTION    CONSTANTLY    NECESSARY.     2  IT 

Emily. — And  it  is  by  arranges  en  :s  of  this  kind,  entire- 
ly mechanical  in  their 
nature,  that  the  mus- 
cles exert  their  pow- 
er, and  produce  those 
varied  movements  re- 
quired in  the  loco- 
motion of  the  body. 
The  study  of  the  ani- 
mal system  might 
give  a  lesson  to  the 
mechanic,  as  well  as 
to  the  philosopher — 
the  man  of  books. 

Dr.  B.— Not  only 
are  the  movements 
of  the  body  produced 
in  this  manner,  but 
also  the  various  atti- 
tudes which  we  as- 
sume, require  the  ac- 
tion of  a  certain  se- 
ries of  muscles. 

Emily.— That  mus- 
cular action  is  neces- 
sary in  running  walk- 
ing, &ic.  is  obvious 
enough,  but  certain- 
ly you  do  not  mean  to  say  that  in  standing  still,  or  lying 
down,  there  is  any  exertion  of  muscular  power  ? 

Dr.  B. — You  think  then,  that  the  body  is  so  con- 
structed, that  when  placed  on  its  feet,  it  will  stand  without 
support  or  exertion.  Do  you  imagine  that  a  lifeless  body 
would  stand  on  its  feet  without  support  ? 

Emily.- — I  acknowledge  I  am  wrong,  but  still  I  do  not 
perceive  how  this  exertion  is  made,  which  keeps  the 
body  upright. 

Dr.  B. — It  is  true  that  the  human  body  is  coHstructed 
19 


218  STANDING. 

for  the  erect  position,  and  that  its  weight  falls  within  the 
base  of  support,  the  feet,  and  therefore  if  formed  of  a 
single  piece  like  a  marble  statue,  would  stand  without  the 
need  of  other  assistance.  But  it  is  to  be  recollected 
that  the  body  is  composed  of  various  pieces,  connected 
together  by  joints  that  are  easily  bent  by  the  superincum- 
bent weight,  and  that  consequently  this  tendency  must  be 
counteracted  by  suitable  provisions.  These  provisions 
are  found  in  the  action  of  the  muscles. 

Emily. — How  is  this — the  muscles  bend  the  joints, 
and  therefore  the  more  strongly  they  act,  the  more  diffi- 
cult will  it  be  for  the  body  to  keep  erect. 

Dr.  B. — There  are  muscles,  not  only  to  bend  the 
joints,  but  others  whose  office  it  is  to  bring  the  limbs 
back  again  to  their  unbent  position.  The  former  are 
ca\\ed  flexors,  the  latter  extensors.  Generally,  the  body 
when  left  without  support  of  any  kind,  has  a  tendency  to 
fall  forward,  and  if  we  examine  the  connexions  of  some 
of  its  parts,  we  shall  immediately  see  the  cause. 

Emily. — I  recollect  you  mentioned  that  the  head 
slightly  preponderated  forward,  and  this  I  suppose,  as- 
sists in  the  general  preponderance  of  the  whole  body  in 
that  direction. 

Dr.  B. — In  standing  therefore,  the  muscles  on  the 
back  part  of  the  neck  are  strongly  exerted  to  maintain 
the  head  erect.  The  weight  of  the  organs  in  the  chest 
and  abdomen,  has  a  tendency  to  carry  it  forward,  which 
is  counteracted  by  the  long  and  powerful  muscles  on  the 
back.  The  whole  weight  of  the  trunk  is  now  transmit- 
ted to  the  hip-joint  which  would  be  inevitably  bent  were 
it  not  prevented  by  muscular  action  ;  thence  it  is  trans- 
mitted to  the  knee  joint  and  finally  to  the  ancle  joint,  both 
which  are  kept  from  bending  by  the  same  means.  So 
that  in  standing  there  is  a  constant  and  wearisome  exer- 
tion of  the  muscles  to  prevent  the  parts  from  bending  on 
each  other,  and  preserve  the  general  equilibrium  of  the 
body. 

Emily. — I  might  have  known  better,  if  I  had  but  re- 


CONTRIVANCE    IN    THE    LEG    OF    BIRDS.  219 

membered  how  fatiguing  it  is,  to  continue  standing  still 
for  any  length  of  time — full  as  much,  I  verily  believe,  as 
to  walk  for  the  same  space  of  time.  But  this  cannot  be 
the  case  with  quadrupeds,  for  the  standing  posture  seems 
to  be  one  of  rest  to  them.  The  horse  after  perfoj  ming 
his  task  seldom  lies  down  immediately,  and  all  day  he 
will  stand  in  his  stall  without  being  fatigued. 

Dr.  B. — Because,  his  body  resting  on  a  wider  base 
of  support,  the  tendency  to  fall  in  any  direction  is  ob- 
viously much  lessened,  and  thus  the  equilibrium  is  pre- 
served by  a  very  little  exertion  of  muscular  power. 

In  some  animals  which  are  sometimes  obliged  to 
stand  for  a  great  length  of  time,  we  find  curious  contri- 
vances for  Assisting  the  action  of  the  muscles.  Thus, 
the  sea-birds,  as  the  heron,  which  wade  upon  the  shores 
of  the  sea  and  in  the  marshes  for  fish  and  reptiles,  their 
natural  food,  had  long  excited  the  curiosity  of  naturalists, 
by  the  length  of  time  in  which  they  would  stand  motion- 
less, expecting  their  prey.  At  last  it  was  found,  that  in 
the  lower  extremity  of  the  thigh-bone  there  is  a  deep 
cavity  into  which  a  corresponding  projection  in  the  leg 
can  be  shut  at  the  pleasure  of  the  animal.  The  thigh 
and  leg  being  thus  firmly  locked  together,  and  to  all  in- 
tents and  purposes,  constituting  but  one  piece,  no  mus- 
cular power  is  necessary  to  keep  them  extended. 

Emily. — I  should  think  some  mechanical  contrivance 
was  needed  by  all  birds,  to  enable  them  to  roost  so  long 
as  they  do  without  loosing  their  hold. 

Dr.  B. — And  such  a  one  is  possessed  by  all  birds, 
and  is  no  less  curious  than  that  just  described,  which  is 
possessed  by  only  a  few.  The  muscle  which  bends 
their  talons,  or  draws  them  together  so  that  they  grasp 
an  object,  coming  from  the  thigh,  passes  over  the  back 
part  of  the  ancle-joint,  or  heel,  proceeds  along  the  foot, 
and  is  inserted  into  the  toes. 

Emily. — So  that  when  the  ancle-joint  is  bent,  as  it 
must  be  when  the  bird  is  perched,  this  muscle  is  bent 
at  the  same  time,  and  the  talons  which  obey  the  con- 


WALKING. 

traction  of  the  muscle,  are  drawn  closely  and  firmly 
around  the  object  which  they  embrace.  Is  it  not  so  ? 

Dr.  B. — Yes ;  and  observe  too,  that  the  greater  the 
weight  of  the  body  by  which  the  muscle  is  bent,  the  stron- 
ger will  be  the  grasp.  In  this  way  they  are  enabled  to 
grasp  a  branch  so  firmly,  as  to  sleep  secure,  even  when 
agitated  by  the  winds. 

Emily. — I  have  often  wondered  how  birds  could  roost 
without  being  liable  at  every  moment  to  lose  their  bal- 
ance, and  tumble  off  in  their  sleep.  But  how  simply 
though  perfectly  is  this  accident  obviated,  by  this  sin- 
gular arrangement.  Still,  some  muscular  exertion  is 
necessary  to  prevent  the  body  from  pitching  forward 
or  backward,  and  I  do  not  see  how  this  ca*n  take  place 
while  the  animal  is  sleeping. 

Dr.  B. — A  certain  degree  of  muscular  strength  in- 
deed, they  do  exert  ;  and  it  is  so  even  with  ourselves. 
When  we  lie  down  to  sleep,  the  limbs  must  either  be 
perfectly  straight,  which  will  require  the  action  of  the 
extensors,  or  bent,  requiring  the  action  of  the  flexors  > 
so  that  whatever  position  we  take,  some  muscles  must  be 
put  into  action.  Birds  are  endowed  with  the  power  of 
making  greater  muscular  exertion  during  sleep,  and  con- 
tinuing it  for  a  greater  length  of  time,  than  man. 

The  most  common  kind  of  progression  used  by  man. 
is  that  of  walking,  and  though  every  body  of  sound  limb 
is  capable  of  performing  this  process,  very  few  indeed 
are  aware  of  the  complicated,  yet  harmonious  series  of 
motions  necessary  to  be  executed  before  a  single  step 
can  be  completed. 

Emily. — I  can  vouch  for  not  making  one  of  that  few, 
for  it  wrould  as  soon  have  entered  my  head  to  ask  how 
I  eat  or  sleep,  as  how  I  walk.  But  I  am  no  less  de- 
sirous of  being  informed  precisely  how  this  process  is 
accomplished. 

Dr.  B. — Suppose  now  a  person  to  be  standing  firm 
and  erect  on  both  feet,  ready  to  take  the  first  step.  His 
first  motion  is  to  throw  the  weight  of  the  body  on  on** 


WALKlNfc    BLINDFOLDED. 

foot ;  secondly,  the  hip,  knee  and  ancle  joints  of  the  other- 
limb  are  all  a  little  bent — this  shortens  the  limb  and  raises 
the  heel ;  thirdly,  the  thigh  is  still  more  bent  on  the  hip— 
this  carries  the  whole  limb  forward;  fourthly,  the  knee  and 
ancle  joints  are  straightened  ;  fifthly,  the  foot  is  brought 
to  the  ground,  the  heel  touching  first  and  then  the  toes. 
To  effect  the  latter  motion,  the  pelvis  roils  upon  the 
other  thigh,  which  continues  immoveable,  carrying  along 
with  it  that  side  of  the  body,  in  the  same  direction  with 
the  limb  that  is  moved.  Thus  far  no  progression  has 
been  made,  because  the  other  part  of  the  step,  the  bring- 
ing up  the  foot  that  is  behind,  is  not  completed.  To  do 
this — supposing  the  left  limb  is  behind  and  the  right  in 
advance — the  left  side  of  the  trunk  is  carried  round 
towards  the  right  and  a  little  forward  at  the  same  time, 
by  the  right  hip  rolling  on  the  right  thigh — this  motion 
throws  the  weight  of  the  body  on  the  right  limb,  which 
is  firmly  and  completely  extended,  excepting  the  ancle 
joint ;  secondly,  the  joints  in  the  left  limb,  which  is  now 
perfectly  straight  and  touching  only  at  the  toes,  are  all 
bent — this  carries  the  limb  forwards  and  brings  it  to  the 
ground,  in  the  same  way  as  the  former  was. 

Emily. — In  this  manner,  the  body  does  not  advance 
iu  a  straight  line,  but  by  a  series  of  oblique  lines  running 
between  two  parallels  from  one  to  the  other,  producing 
a  zig-zag  course. 

Dr.  B. — And  in  order  that  these  oblique  movements 
may  be  equal  to  one  another,  so  as  not  to  carry  the  body 
out  of  the  straight  direction,  our  constant  attention  is  re- 
quired. Did  you  never  observe  how  irregular  a  per- 
son's course  is,  when  walking  blind-folded  ? 

Emily. — I  have  seen  persons  attempt  to  walk  from 
one  end  of  a  field  to  the  other  blind-folded,  but  with  one 
or  two  exceptions,  they  were  always  brought  up  by  the 
fence  at  the  sides ;  sometimes  they  even  turned  com- 
pletely round,  and  came  back  to  the  very  spot  whence 
>they  started.  It  seems  to  be  quite  impossible  with  the 
19* 


222  LEAPING. 

eyes  blinded,  to  reach  a  spot  at  quite  a  short  distance 
from  the  starting-point. 

Dr.  B. — In  ascending  an  inclined  plain,  or  a  flight 
of  steps,  greater  muscular  exertion  is  required  than  in 
walking  on  a  level,  because  when  the  foot  first  moved 
is  brought  to  the  ground,  it  is  bent,  instead  of  being 
straight ;  consequently,  when  the  other  foot  is  brought 
forward  to  the  same  level,  the  first  limb  must  be  straight- 
ened with  the  whole  weight  of  the  body  resting  upon  it, 
in  order  that  the  body  may  be  raised  to  the  erect  position. 

Emily. — And  it  is  this  repeated  exertion  of  raising 
the  whole  weight  of  the  body  on  one  leg,  which  produces 
the  fatigue  we  soon  feel  in  walking  up  a  hill  or  a  flight  of 
steps,  is  it  not  ?  But  the  same  fatigue  is  experienced  in 
descending  a  hill,  though  perhaps  not  quite  so  soon  ;  I 
do  not  exactly  understand  how  this  should  be. 

Dr.  B. — Here,  in  bringing  down  the  foot  first  moved 
to  a  level  lower  than  the  one  on  which  the  foot  behind 
stands,  the  latter  is  obliged  to  sustain  the  whole  weight 
of  the  body  with  the  joints  all  bent,  which,  you  know,  re- 
quires considerable  exertion. 

Eimly. — The  peculiar  difference  then  between  ascend- 
ing and  descending  an  inclined  plain,  is,  that  in  the  former 
the  limb  is  to  be  straightened  with  the  whole  weight  of 
the  body  resting  on  it,  and  in  the  latter,  it  is  to  be  bent, 
while  sustaining  the  same  weight.  Arn  I  not  right  r 

Dr.  B. — Yes,  and  quite  a  good  distinction  it  is.  In 
leaping,  all  the  joints  are  put  into  a  state  of  flexion,  and 
then  extended  by  a  sudden  and  powerful  motion.  The 
force  used  in  extending  the  limbs  is  so  much  greater 
than  is  necessary  for  overcoming  the  weight  of  the  body, 
that  it  is  carried  from  the  ground,  and,  in  consequence 
of  the  impulse  received  from  the  feet,  in  a  forward  di- 
rection. This  sudden  straightening  is  not  confined  to 
the  limbs  merely,  but  takes  place  in  the  back,  and  you 
can  easily  conceive  how  much  this  motion  is  assisted  by 
the  sudden  extension  of  the  spine,  when  you  recollect 
that  all  the  vertebrae  are  separated  from  one  another  by 


RUNNING*  223 

a  thick  cartilage,  possessing  very  great  elasticity.  In 
fishes,  whose  motions  require  a  great  elasticity,  this  car- 
tilage is  exceedingly  thick.  In  the  great  basking  shark, 
to  increase  this  elasticity  of  the  spine,  there  is  in  the 
centre  of  the  cartilage,  a  cavity  containing  a  small  quan- 
tity of  water.  This  is  so  strongly  compressed,  that  in 
one  instance  when  the  cartilage  was  punctured,  it  was 
projected  in  a  large  stream  four  feet  high. 

Emily. — It  is  by  this  sudden  and  powerful  extension 
of  the  body,  I  suppose,  that  salmon,  trout,  and  other 
fishes  are  able  to  ascend  waterfalls  and  other  obstacles 
to  their  course,  though  many  feet  high. 

Dr.  B. — Yes,  and  this  fact  shows  very  forcibly  the 
great  elasticity  of  their  spine. 

Leaping  is  the  method  of  progression  used  by  ani- 
mals whose  anterior  and  posterior  extremities  are  of  dis- 
proportionate length.  The  hare,  rabbit,  jerboa,  and 
squirrel,  whose  hind  legs  are  so  much  longer  than  the 
others,  as  to  unfit  them  from  running,  advance  by  a  suc- 
cession of  leaps. 

Emily. — What  wonderful  leaps  a  frog  will  take. 
Grasshoppers,  whose  legs  are  very  long  in  proportion  to 
their  body,  will  makte  astonishing  leaps  for  such  little 
creatures.  I  have  seen  it  calculated  that  the  height  to 
which  a  grasshopper  leaps,  is  to  the  length  of  its  body, 
as  200  to  1 ,  and  a  flea,  I  believe,  leaps  still  farther  and 
with  greater  velocity. 

Dr.  B. — The  leaping  powers  of  the  flea  are  wonder- 
ful, and  have  been  thought  worthy  to  be  made  the  subject 
of  a  learned  work  by  Roberval,  entitled  de  saltu  pulicis, 
or  leaping  of  the  flea. 

Running  seems  to  be  a  combination  of  both  walking 
and  leaping.  It  differs  from  the  latter,  for  the  reason 
that  the  feet  do  not  move  together,  and  from  the  former, 
because  the  foot  behind  is  raised  from  the  ground  before 
the  other  has  reached  it ;  so  that  during  every  step,  the 
body  is  suspended  for  a  moment  without  any  support. 


INFLUENCE    OF    HABIT    OVEK   THE    MUSCLES, 

Running,  therefore,  may  be  considered  as  a  succession 
of  short  leaps  with  one  foot.  The  leaps  are  made  in 
rapid  succession,  and  the  toes  only  come  to  the  ground. 
Such  are  a  few  of  the  principal  methods  of  progression 
made  use  of  by  man ;  some  others  are  seen  in  the  inferi- 
or animals,  but  it  is  rather  foreign  to  our  purpose  to  de- 
scribe them. 

Of  all  the  organs  in  the  animal  economy,  the  muscles 
are  most  under  the  control  of  habit, — habit  even  is  neces- 
sary before  the  simplest  and  smallest  efforts  are  easily 
performed.  When  we  consider  how  difficult  it  is  to 
perform  almost  any  motion  for  the  first  time,  it  is  truly 
astonishing  to  see  how  much  may  be  finally  accomplished 
by  perseverance  in  a  constant  and  regular  habit. 

Emily. — I  am  perfectly  aware  of  this.  I  recollect  when 
I  contrasted  the  accuracy  a.id  rapidity  with  which  the 
fingers  of  an  accomplished  player  move  over  the  keys  of 
the  piano,  with  my  own  awkward  first  attempts,  I  could 
not  believe,  what  I  am  well  convinced  of  now,  that  habit 
would  in  time  make  that  perfectly  easy,  which  appeared 
to  me  the  result  of  a  peculiar  gift  of  nature. 

Dr.  B. — It  is  not  only  the  muscles  of  the  fingers,  but 
those  of  every  other  part  of  the  body  over  which  habit 
has  a  wonderful  influence.  We  have  only  to  look  into  a 
circus,  and  see  men  dancing  on  slack  ropes  with  as  much 
ease  apparently,  as  on  an  elastic  floor,  standing  tip-toe  on 
a  horse's  back,  and  while  he  is  going  at  full  speed,  jump- 
ing through  a  hoop  under  which  he  passes  and  alighting 
upon  his  back  on  the  other  side,  and  many  other  feats 
equally  astonishing,  to  be  thoroughly  convinced  of  this. 

Emily. — In  truth  we  may  not  go  so  far  as  that,  for  I 
understood  that  some  wonderful  things  are  done  now-a- 
days  at  the  gymnasia,  not  by  men  who  make  a  business 
of  it,  but  by  staid  and  grave  citizens,  purely  for  pastime 
and  exercise. 

Dr.  B. — Yes — Gymnasia  are  institutions  now  revi- 
ving in  the  world,  for  the  purpose  of  developing  that 


GYMNASTIC  EXERCISES.  225 

muscular  power,  not  one  twentieth  of  which  is  called  into 
use  in  the  ordinal y  occupations  of  life.  It  is  quite  as- 
tonishing to  see  how  rapidly,  and  how  much  of  this  dor- 
mant power  is  awakened,  by  the  various  exercises  of 
climbing,  jumping,  pulling,  leaping,  &tc.  which  are  per- 
formed at  these  places. 

Emily. — But  I  really  do  not  comprehend  what  great 
object  is  obtained  after  all,  by  having  every  muscle  in 
the  body  carried  to  its  maximum  of  developement. 
People  are  not  going  to  get  their  living  by  clirribiug,  or 
running  for  a  wager,  and  if  exercise  be  the  only  object 
in  view,  it  appears  to  me,  that  sufficient  for  all  necessary 
purposes,  may  be  obtained  with  less  trouble  and  in  less 
time. 

Dr.  B.— Gymnastic  exercises  will  not  indeed  give  a 
man  a  livelihood,  nor  does  any  one  suppose  that  they 
are  absolutely  necessary  to  keep  him  in  existence,  for 
many  men  enjoy  excellent  health  and  live  to  a  good  old 
age,  without  ever  having  entered  a  gymnasium.  Behold 
the  light  in  which  these  exercises  are  to  be  viewed  in  order 
to  perceive  their  utility  ; — the  human  constitution  is  con- 
tinually subjected  to  the  operation  of  a  multitude  of  caus- 
es, the  effects  of  which  are,  to  weaken  its  powers,  en- 
gender disease,  and  shorten  its  duration.  It  is  impossi- 
ble to  avoid  these  causes  for  they  exist  in  the  air  that  we 
breathe,  in  the  soil  that  we  tread  on,  and  the  substances 
that  we  take  into  our  bodies,  and  our  only  recourse  is  to 
make  use  of  the  means  proper  for  withstanding  their  ef- 
fects. The  most  obvious  means — the  only  one  which 
reason  dictates,  is  to  strengthen  and  develope  to  the  ut- 
most those  very  powers  with  which  nature  endowed  our 
bodies,  to  enable  them  to  resist  the  influence  of  the  nox- 
ious agents  by  which  they  are  encompased.  The  body 
that  is  made  strong  and  robust  by  habits  of  temperance 
and  exercise,  is  the  best  adapted  to  withstand  the  effects 
of  those  exposures  to  which  every  person  is  more  or  less 
liable.  This  is  the  tendency  of  gymnastic  exercises,  and 
this  is  their  utility. 


226  GYMNASTIC    EXERCISES. 

Emily. — This  is  indeed  a  light  in  which  I  never  view- 
ed the  matter  before,  and  I  humbly  plead  guilty  to  ill- 
grounded  prejudice. 

Dr.  B. — To-morrow  we  shall  speak  of  sleep,  rela- 
tions of  the  functions,  and  death. 


SLEEP  CONFINED  TO  THE  ORGANIC  FUNCTIONS.  227 


CONVERSATION  IX. 


Sleep — necessary  quantity  varied  by  age,  habit,  tempera- 
ment, fyc. — state  of  the  brain  during  sleep — dreaming, 
somnambulism — influence  of  sleep  on  the  other  func- 
tions— influence  of  habit  on  the  animal  and  organic 
functions — difference  in  the  origin  of  these  functions 
— relations  and  mutual  influence  of  the  functions — 
laws  of  existence — death. 

Emily. — To  day  you  are  to  speak  of  sleep — that  re- 
pose in  which  man  participates  with  every  other  mem- 
ber of  the  animal  kind.  It  is  singular  how  necessary  the 
periodical  return  of  this  state  is  to  the  animal  system,  in- 
somuch that  to  a  person  in  good  health,  it  is  one  of  the 
most  difficult  things  to  keep  awake  twenty  four  hours  in 
succession.  I  have  heard  the  animal  system  aptly 
compared  to  a  watch  which  required  winding  up  once  in 
twenty  four  hours — and  this  winding  up  is  sleep. 

Dr.  ~B. — The  comparison  is  hardly  just,  if  by  animal 
system  you  mean  the  constitution  generally,  for  sleep  is 
confined  to  what  we  have  called  the  organs  of  animal 
life.  The  functions  of  organic  life  are  not  suspended  in 
this  way ;  respiration,  circulation,  secretion,  &LC.  are  in 
continual  action.  The  organs  of  animal  life  require 
frequent  intervals  of  repose,  to  recruit  their  exhausted 
powers,  and  in  this  state  of  inactivity,  the  individual 
seems  to  enjoy  a  mere  vegetative  existence. 

.Emily. — It  has  appeared  to  me  a  little  surprising  that 


228  NECESSARY    QUANTITY    OF    SLEEP. 

"  nature's  sweet  restorer,"  though  plunging  the  restless 
and  active  powers  of  the  soul  into  a  state  resembling  as 
nearly  as  we  can  conceive,  that  of  annihilation,  should  yet 
be  attended  with  a  pleasure  from  which  we  part  with  re- 
luctance. 

Dr.  B. — It  seems  to  be  a  law  of  the  animal  economy 
that  repose  should  be  attended  with  pleasure,  for  the 
same  reason  th'it  the  gratification  of  our  appetites  is.  The 
quantity  of  sleep  required  greatly  varies  according  to  age, 
temperament  and  habits.  In  early  childhood,  and  in  the 
second  childhood  of  old  age,  where  the  small  share  of  irri- 
tability is  soon  exhausted,  and  nature  demands  frequent 
repose,  much  of  the  time  is  spent  in  this  state.  It  may 
be  considered  generally,  that  the  quantity  of  sleep  neces- 
sary to  good  health,  gradually  diminishes  from  birth  till 
the  age  of  mature  manhood  ;  from  that  period  till  death, 
its  necessity  as  constantly  increases.  The  young  stu- 
dent knows  how  difficult  it  is  for  him  to  continue  his  ap- 
plication for  a  space  of  time  which  the  veteran  scholar 
will  nearly  double,  without  the  least  inconvenience.  It 
is  true,  when  ambition  or  some  other  powerful  motive 
spurs  him  on,  he  may  leave  his  bed  early  and  burn  his 
lamp  late,  but  the  unhappy  effects  that  so  often  follow 
such  exertions,  show  full  well  how  unnatural  they  are. 

In  maturer  life  when  the  vital  powers  are  not  so  soon 
exhausted,  the  system  is  capable  of  much  greater  exer- 
tions. Hear  the  declaration  of  Buffon,  when  speaking 
of  those  moments  of  abstraction  and  rapture  which  ac- 
company the  meditations  of  the  great  genius,  and  consti- 
tute his  true  hours  of  production  and  composition, — "  I 
have  spent  fourteen  or  fifteen  hours  successively,  at  my 
desk,  and  still  been  in  a  state  of  pleasure." 

Emily. — I  have  heard  too  that  Mr. though  now 

nearly  seventy  years  old,  generally  spends  fourteen  hours 
every  day  in  close-study. 

Dr.  B. —  The  influer.ee  of  habit  also,  in  determin- 
ing the  necessary  quantity  of  sleep,  is  considerable. 


RECRUITING    POWER    OF    SLEEP. 

Some,  from  this  cause,  require  eight  or  ten  hours,  while 
others  are  perfectly  contented  with  half  that  quantity. 
The  slight  quantity  of  sleep  that  sometimes  has  been 
found  to  be  sufficient,  is  almost  incredible.  The  cele- 
brated General  Pichegru  who  commanded  the  armies 
of  France  during  her  revolution,  declared  to  his  physi- 
cian, that  in  the  course  of  hi's  active  campaigns,  he  had 
not  for  a  whole  year  more  than  one  hour's  sleep,  upon 
an  average,  in  twenty  four. 

Emily. — It  is  hardly  possible  to  conceive  how  one  hour 
can  afford  the  same  refreshment  which  others  find  it  dif- 
ficult to  obtain  in  six  times  that  space. 

Dr.  B. — The  refreshment  produced  by  sleep  does  not 
seem  to  be  in  exact  proportion  to  its  duration.  The  first 
portion  of  sleep  is  undoubtedly  most  refreshing;  it  be- 
comes less  so  the  longer  it  is  continued,  and  if  carried  too 
far  is  followed  by  effects  of  quite  a  contrary  nature. 

Emily. — The  old  proverb  then,  "  one  hour's  sleep  be- 
fore mid-night  is  worth  two  after,"  is  founded  in  truth. 

Dr.  B. — Sleep  is  not  a  state  of  mere  inaction,  but 
one  in  which  exhausted  energies  are  recruited,  and  or- 
ganic losses  repaired.  "  The  powers  of  the  sensorium, 
seem  to  be  wound  up  as  it  were,  in  the  first  periods  of 
sleep  5  and  a  great  part  of  the  refreshment  in  later  hours, 
seems  more  imputable  to  the  simple  repose  of  the  or- 
gans, than  to  the  recruiting  powers  peculiar  to  sleep." 
Some  people  require  after  dinner,  a  nap  oi  fifteen  or 
twenty  minutes,  after  which  they  can  proceed  to  their 
business  with  fresh  alacrity ;  whereas,  a  deprivation  of 
their  accustomed  nap  renders  them  drowsy  and  spiritless 
for  the  rest  of  the  day.  It  is  related  of  the  European 
missionaries  in  China,  that  being  obliged  by  their  duties 
to  take  as  little  time  as  possible  for  that  sleep  in  the  mid- 
dle of  the  day  which  is  rendered  necessary  by  the  nature 
of  the  climate,  they  laved  down  with  a  brass  ball  in  their 
hand,  and  under  it  a  brass  basin.  The  moment  they 
dropped  entirely  asleep,  the  ball  fell  from  th£ir  hand  into 
20 


230  NATURE    0F    SLEEP. 

the  basin  and  the  noise  waked  them  up,  but  the  refresh- 
ment thus  gained  was  found  sufficient  for  their  purpose.* 

Emily. — And  does  not  the  refreshment  procured  by 
sleep  depend  considerably  on  the  state  of  the  rnind  ?  I 
have  found  sometimes  when  I  have  retired  to  rest  with 
my  mind  deeply  occupied  with  any  subject,  that  my 
sleep  is  restless  and  disturbed  by  unpleasant  dreams. 

Dr.  B. — Undoubtedly  it  does — sound,  refreshing 
sleep  requires  that  the  mind  should  be  free  from  care, 
anxiety  and  passion,  and  wearied  in  some  degree  by  the 
employments  of  the  day.  The  physical  powers  should 
also  be  fitted  to  repose  by  means  of  suitable  exercise. 
Do  you  recollect  that  much-quoted  passage  in  Shak?- 
peare : — 

"  I  know  'tis  not  the  sceptre  and  the  ball, 

The  sword,  the  mace,  the  crown  imperial. 

The  intertissued  robe  of  gold  and  pearl, 

The  farsed  title  running  'fore  the  king, 

The  throne  he  sits  on,  nor  the  tide  of  pomp 

That  beats  upon  the  high  shore  of  the  world ; 

No,  not  all  these,  thrice  gorgeous  ceremony, 

Not  all  these,  laid  in  bed  majestically, 

Can  sleep  so  soundly  as  the  wretched  slave, 

Who  with  a  body  filled  and  vacant  mind 

Gets  him  to  rest,  crammed  with  distressful  bread, 

who,  from  the  rise  to  set, 

Sweats  in  the  eye  of  Phrcbus,  and  all  night 
Sleeps  in  Elysium." 

HENRY  V.  Act  IV.   Scene  I. 

Emily. — Can  sleep,  Dr.  B.,  be  strictly  considered  as 
the  repose  of  all  the  organs  of  animal  life  ?  You  know 
we  are  frequently  changing  our  position  in  sleep,  which 
evidently  indicates  the  exercise  of  the  will,  and  conse- 
quently that  part  of  the  brain  with  which  the  will  is  con- 
nected. We  likewise  see  and  hear  sometimes,  and  the 
intellectual  faculties  are  frequently  as  active  and  acute  as 
in  our  waking  moments. 

Dr.  B. — Complete  sleep,  or  the  repose  of  all  the 

*T.  Sully,  the  painter,  one  of  his  fiiends  has  informed  me,  gets 
his  sleep  in  this  way— using  a  key  however  instead  of  a  ball. 


SOMNAMBULISM. 


ofgaris  of  animal  life,  I  know,  is  rarely  enjoyed.  Sleep 
is  most  commonly  partial  ;  some  portions  of  the  nervous 
system  are  at  rest,  while  others  enjoy  their  wonted  ac- 
tivity. I  have  already  showed  you  how  the  sensorial 
power  might  be  active,  while  the  nervous,  is  in  a  state 
of  repose.  The  exercise  of  the  intellectual  powers 
seems  to  be  rather  impaired  or  weakened,  than  entirely 
suspended,  either  in  one  or  all.  This  is  proved  by  the 
incoherence  and  irregularity  of  our  ideas  in  sleep  ;  they 
float  confusedly  through  the  mind  without  continuity  or 
distinctness,  and  like  the  changing  figures  of  a  phantas- 
magoria, are  ever  assuming  another  shape  and  name. 
The  mind  in  its  stupor  grasps  them  feebly,  and  in  at- 
tempting to  compare  them  together,  brings  them  into 
awkward  and  grotesque  combinations. 

Emily.  —  And  yet  you  know  that  sometimes  our  ideas 
m  sleep  are  quite  original,  and  our  reasonings  remarka- 
bly logical. 

Dr.  B.  —  There  are  instances  it  is  true,  in  which  our 
sleeping  thoughts  seem  to  have  a  regularity,  strength, 
and  vividness  unknown  in  onr  waking  moments  ;  but 
probably  we  are  the  subjects  of  a  little  deception  in  this 
respect.  When  we  call  to  mind,  as  we  sometimes  can, 
the  jokes  that  "set  the  table  in  a  roar"  ;  the  argument 
that  appeared  irresistible  ;  and  the  verses,  redolent  with 
the  odour  of  true  genius,  how  stale,  flat  and  insipid  they 
appear. 

The  character  of  our  dreams  is  frequently  determin- 
ed by  the  thoughts  that  have  deeply  engrossed  the  mind 
during  the  day.  The  ambitious  man  dreams  of  power 
and  laurels  ;  the  mathematician  makes  calculations  ;  the 
poet  writes  verses  ;  and  the  gourmand  devours  heca- 
tombs of  good  things. 

Emily.  —  There  is  a  state  of  mind  during  sleep,  called 
somnambulism,  I  believe,  about  which  there  are  some 
curious  facts  —  pray  tell  me  what  it  actually  is. 

Dr.  B.  —  It  can  hardly  be  called  a  state  of  sleeping  or 
waking,  though  we  are  unable  to  explain  all  its  phenom- 


232  THE    TWO    LIVES;. 

ena.  Somnambulists,  or  sleep-walkers  after  sleeping 
soundly  a  short  time  get  up  from  their  bed,  dress  them- 
selves, and  go  about  their  usual  occupations.  They  have 
been  known  to  converse,  read,  compose,  &c.  return  to 
their  bed,  and  wake  in  the  morning  utterly  unconscious 
of  what  has  happened.  The  mind  seems  to  be  in  a. 
state  nearly  akin  to  that  known  by  the  name  of  revery  ; 
the  eye  and  ear  remain  open,  but  the  impressions  made 
on  the  mind  are  confused  and  indistinct,  because  the 
rnind  is  here,  as  in  common  sleep,  in  a  sort  of  stupor. 
For  the  same  reason,  though  they  have  perfect  command 
of  the  voluntary  motions,  yet  they  are  just  as  likely  to 
throw  themselves  from  the  window,  and  undertake  di- 
vers perilous  things,  as  to  do  any  thing  else.  This  is  all 
we  know  of  sumnambulism. 

Emily. — Does  not  sleep  possess  some  influence  over 
the  organic  functions  ?  It  seems  hardly  possible  that 
they  should  go  on  with  the  same  vigor,  as  when  they 
are  accompanied  by  the  animal  functions. 

Dr.  B. — They  do  not ;  the  circulation  is  less  frequent, 
respiration  heavier,  and  digestion  slow  and  difficult.  All 
these  phenomena  strongly  proclaim,  how  complete  is  the 
passive  and  even  vegetable  condition,  during  the  period- 
ical repose  and  renovation  of  nature. 

Here  ends  our  history  of  the  functions  of  animal  and 
organic  life.  You  have  seen  how  distinct  they  are  in  the 
animal  economy,  and  yet  how  uniformly  their  mutual  de- 
pendence is  maintained. 

Emily. — Yes— we  seem  to  enjoy  two  lives,  in  a  phy- 
siological sense  ;  by  one,  we  grow  up  and  hold  our  ex- 
istence ;  by  the  other,  we  operate  on  the  external  world 
and  draw  thenceforth  the  materials  of  happiness,  or  mis- 
ery. By  one,  we  constitute  an  independent,  insulated 
being ;  by  the  other,  we  enter  the  grand  chain  of  exis- 
tence, a  necessary  and  permanent  link. 

J)r.  J5. — The  animal  functions  we  have  seen  require 
intervals  of  repose  ;  the  organic  functions,  on  the  contrary, 
are  incessantly  going  on — let  respiration  or  circulation 
once  cease,  and  existence  is  at  an  end, 


DIFFERENCE   IN   THE    ORGANS  OF  THE  TWO  LIVES. 

We  have  seen  also  how  differently  the  two  lives  are 
affected  by  habit.  The  very  degree  of  perfection  to 
which  the  animal  life  attains,  depends  chiefly  on  educa- 
tion ;  the  organic  is  but  very  little  under  its  control.  By 
habit,  we  have  seen  that  the  motive  powers  are  carried 
to  their  highest  degree  of  energy  and  developement.  It 
is  the  same  too,  with  the  sensations.  By  long  continued 
training,  the  senses  arrive  to  a  state  of  acuteness  un- 
known in  the  natural  condition.  The  effect  of  sensa- 
tion on  the  mind  is  also  equally  under  the  control  of 
habit,  though  in  a  different  way.  By  long  continued 
repetition,  the  most  vivid  and  poignant  sensations,  con- 
stantly grow  weaker  in  their  impressions,  till  at  last,  they 
are  scarcely  recognized  by  the  mind.  The  most  beau- 
tiful scenes  of  nature  or  art,  after  a  time,  pall  upon  the 
sight,  and  the  most  melodious  sounds  fall  heavily  on  the 
ear.  From  the  same  cause  too,  sensations  which  are  at 
first  attended  with  pain  or  disgust,  become  in  the  end 
delightful  sources  of  enjoyment. 

Emily. — But  by  no  means  can  we  habituate  the  blood 
to  move  faster  or  slower  through  the  vessels,  or  the  res- 
piratory organs  to  act  quicker  and  more  vigorously. 

Dr.  B. — In  their  origin  also,  the  two  lives  differ.  The 
organic,  we  find  in  full  play  and  perfection  at  the  mo- 
ment of  birth.  The  animal,  on  the  contrary,  is  at  this 
period,  but  imperfectly  developed  ;  weak,  feeble,  indis- 
tinct at  first,  time  is  required  for  its  complete  develope- 
ment. 

Another  striking  difference  between  the  two  lives,  is 
not  to  be  passed  over — it  regards  the  form  and  position 
of  their  organs.  In  the  animal  life,  the  organs  are  sym- 
metrical ;  and  are  either  in  pairs,  each  being  perfectly 
similar  to  the  other,  and  placed  on  each  side  of  the  me- 
dian line  at  equal  distances  from  it,  or  single,  placed  di- 
rectly over  that  line,  and  divided  by  it  into  two  sym- 
metrical halves. 

Emily. — Let   me  interrupt  you  one  moment  to  ask 
what  you  mean  by  the  median  line  ? 
20* 


«234     MUTUAL    DEPENDENCE    OF    THE    FUNCTIONS. 

Dr.  B. — It  is  an  imaginary  line  passing  through  the 
middle  of  the  body  in  a  longitudinal  direction,  dividing 
it  into  two  similar  halves. 

Emily. — And  on  this  line  are  placed  the  nose,  mouth, 
tongue,  &ic.  and  on  each  side  of  it  are  ranged  the  organs 
of  vision,  hearing,  &;c. 

Dr.  B. — The  organs  of  organic  life  show  none  of 
this  symmetry.  They  are  irregular  in  their  form,  and 
situated  without  any  regard  to  the  median  line.  The 
stomach,  liver,  heart  and  spleen  are  placed  in  this  man- 
ner, and  their  halves  bear  no  resemblance  to  each  other. 

We  have  now  gone  through  with  the  functions  of  ani- 
mal existence ;  we  have  examined  them  in  the  various 
classes  of  animals,  and  observed  their  points  of  resem- 
blance and  difference.  As  yet,  however,  we  have  not 
spoken  particularly  of  their  mutual  relations,  influence, 
and  dependence,  and  the  laws  which  regulate  their  com- 
binations. As  we  have  traced  them  separately  and  in 
detail  from  one  class  to  another,  we  have  seen  them 
constantly  undergoing  some  modification  or  other,  and  to 
one  therefore  who  is  but  imperfectly  acquainted  with  the 
subject,  it  would  seem  that  by  combining  together  all 
these  modifications  in  an  arbitrary  manner,  we  could 
vary  to  infinity  the  structure  of  organic  beings. 

Emily. — Certainly  ;  we  should  only  have  to  alter  the 
condition  of  a  single  function,  no  matter  how  little,  leav- 
ing all  the  rest  unchanged,  to  have  a  specifically  differ- 
ent being.  For  instance,  if  we  change  the  structure  of 
the  digestive  organs,  we  have  a  different  animal,  whether 
we  alter  those  of  respiration,  circulation,  sensibility,  &LC. 
or  not. 

Dr.  B. — But  such  combinations  as  these  which  at 
first  sight  appear  possible,  do  not  exist  in  nature.  For 
it  must  be  recollected  that  each  organ  has  not  only  its 
peculiar  function  to  perform  in  the  animal  economy,  but 
that  it  contributes  with  all  the  rest  to  the  production  of  a 
common  object.  Now,  this  is  effected  not  by  joining 
their  results  together  and  making  a  sum  total,  but  by 


CORRESPONDENCE  OF  THE  FUNCTIONS.    236 

their  mutual  and  necessary  influence,  which  requires 
between  them  a  certain  correspondence  of  condition  and 
harmony  of  action.  The  condition  of  one  function  will 
determine  to  a  certain  extent  the  condition  ol  all  the  rest, 
because  each  requires  the  aid  of  all  the  rest  in  the  per- 
formance of  its  destined  office. 

Emily. — We  cannot  then  change  the  condition  of  the 
digestive  organs,  without  making  correspondent  altera- 
tions in  all  the  other  organs.  1  see  now  very  clearly 
that  organization  will  not  admit  of  that  immense  variety 
of  forms,  of  which  it  at  first  sight  seemed  capable. 

J)r.  B. — Respiration,  for  instance,  necessarily  re- 
quires the  circulation  of  the  blood,  and  this  must  not  be 
too  quick  nor  too  slow,  but  in  direct  accordance  with  the 
condition  of  the  respiratory  organs.  The  circulation  is 
maintained  by  the  action  of  the  heart  and  blood-vessels — 

Emily. — And  these  require  the  aid  of  the  nervous 
power  which  is  the  cause  of  their  motions,  and  the  ner- 
vous system  depends  for  its  activity  on  the  circulation 
and  respiration.  I  do  not  see  but  this  influence  revolves 
in  a  circle — it  is  impossible  to  find  a  beginning  or  end. 

Dr.  B.—l  need  not  mention  to  you  how  necessary 
— how  indispensable  in  fact — is  this  correspondence  and 
harmony  of  condition  to  the  existence  of  a  living  being, 
and  how  completely  any  general  result  would  be  frustra- 
ted, by  an  arbitrary  and  heterogeneous  assemblage  t)f 
functions. 

Emily. — It  requires  truly,  no  uncommon  penetration 
to  see  how  useless  would  be  the  power  of  sensibility  for 
instance,  were  it  not  aided  constantly  by  the  muscular 
power.  What  would  be  the  advantage  of  the  sense  of 
touch,  could  we  not  turn  our  hands  towards  palpable 
objects  ?  of  seeing,  if  we  could  not  turn  the  head  or  eyes 
in  every  direction  ?  Of  what  avail  would  be  a  great 
degree  of  activity  in  the  respiratory  organs,  if  the  circu- 
lation were  feeble  ?  of  strong  and  active  powers  of  di- 
gestion, if  the  possessor  were  unprovided  with  means  for 
taking  its  proper  food  ?  What  would  be  the  utility  of 


236  RELATION    OF    RESPIRATI6N    WITH    CIRCULATION. 

high  intellectual  endowments,  if  their  exercise  were  ren- 
dered null  and  void  by  other  incompatible  conditions. 
Dr.  B. — It  is  on  this  mutual  dependence  of  the  func- 
tions and  the  aid  they  reciprocally  give  and  receive,  that 
are  founded  the  laws  which  regulate  the  combinations 
of  organs  in  the  animal  economy — laws,  says  Cuvier, 
"  which  have  their  origin  in  a  necessity  equal  to  that  of 
mathematical  or  metaphysical  laws."  For  if  the  condi- 
tion of  one  organ  or  set  of  organs  be  modified  in  a  man- 
ner incompatible  with  a  corresponding  modification  in 
the  other  organs,  it  is  very  evident  that  being  could  not 
exist.  If  we  take  one  of  the  functions  separately,  and 
assuming  it  as  a  standard  of  comparison,  observe  the  re- 
lations of  the  others  with  it,  we  shall  see  a  little  more 
distinctly  how  they  are  all  made  to  conform  to  it. 

Emily. — But  you  do  not  mean  certainly  that  any  one 
can  regulate  the  conditions  of  the  others,  because  the 
influence  would  then  have  a  beginning  and  an  end. 

Dr.  B. — Very  true,  but  what  I  have  said  is  not  in- 
compatible with  the  idea,  that  the  conditions  of  the 
organs  instead  of  being  regulated  by  a  particular  one, 
are  governed  by  each  other. 

Emily. — Well,  then,  to  begin  your  comparison — which 
organ  shall  you  take  for  the  common  standard  ?  Sup- 
pose they  are  the  organs  of  respiration. 

Dr.  B. — It  is  almost  immaterial  which  we  take,  but  as 
respiration  is  a  function  o(  the  first  importance,  it  will 
answer  our  purpose  as  well  as  any  other.  In  the  first 
place  then  let  us  see  its  relations  with  circulation.  In 
the  higher  animals  where  respiration  is  performed  by 
lungs,  the  circulation  is  provided  with  a  double  heart  by 
which  the  blood  is  impelled  to  the  body  and  lungs.  Of 
the  three  classes  of  animals  in  which  this  kind  ol  respira- 
tion exists,  the  Birds  possess  it  in  the  greatest  quantity 
and  activity.  Their  inspirations  are  made  more  frequent- 
ly, and  their  organs  have  greater  extent  comparatively, 
than  in  the  mammiferous  animals.  The  circulation  has 
a  correspondent  degree  of  activity  ;  in  no  other  animals 


RELATION    OF    RESPIRATION    WITH    THE    MUSCLES.  237 

are  the  pulsations  of  the  heart  so  rapid  and  so  frequently 
repeated.  In  Reptiles,  we  have  seen  that  respiration  is 
quite  inactive  and  Jeeble,  and  they  can  dispense  with  it 
for  a  great  length  of  time.  See  how  perfectly  in  accord- 
ance with  this  condition  is  their  circulation. 

Emily. — The  pulsations  of  the  heart  are  quite  slow 
and  unfrequent,  and  only  half  of  the  blood  sent  to  the 
lungs  requires  its  action,  for  the  other  half  has  just  re- 
turned thence,  and  needs  no  change. 

Dr.  B. — In  Fishes,  respiration  is  performed  by  gills 
which  separate  the  air  from  the  Water,  and  owing  to  this 
disadvantage,  greater  activity  of  both  the  respiration  and 
circulation,  is  necessary  to  produce  a  given  result. 

In  Insects,  the  air  enters  the  body  by  numerous  pores, 
not  by  a  particular  set  of  organs  ;  of  course  neither  heart 
nor  blood-vessels  aie  required  to  transmit  the  blood  to 
these  organs. 

The  relations  between  respiration  and  muscular  mo- 
tion are  exceedingly  obvious  and  well  defined.  The 
quantity  and  activity  of  one  are  generally  proportional  to 
the  quantity  and  activity  of  the  other,  for  one  of  the 
principal  uses  of  respiration,  is  to  reanisnate  the  muscular 
power. 

Emily. — And  is  not  this  the  reason  why  the  respira- 
tion is  always  accelerated  when  we  are  taking  exercise,, 
or  performing  any  task  which  requires  considerable  ex- 
ertion of  muscular  power.  Observe  too,  how  a  dog  or 
horse  pants,  after  running  violently,  or  for  any  length  of 
time. 

Dr.  JB. — This  is  the  reason,  undoubtedly.  In  the 
birds  and  mammiferous  animals  which  have  the  function 
of  respiration  developed  to  its  highest  degree  of  excel- 
lence, the  muscular  power  is  capable  of  the  greatest  and 
longest-continued  exertions.  Birds,  in  which  we  just 
observed  that  the  respiratory  function  existed  in  its 
greatest  perfection,  are  almost  always  in  the  air,  and  the 
locomotive  feats  which  they  sometimes  perform  are  al- 
most incredible. 


238  RELATION  OF  RESPIRATION  WITH  THE  NERVES 

Emily. — Such  constant  exertions  must  necessarily  be 
attended  by  a  great  expenditure  of  power,  and  therefore 
a  corresponding  activity  of  those  organs,  whose  function 
it  is  to  purify  and  renovate  the  fluid  from  which  it  is  sup- 
plied, is  also  required. 

Dr.  B. — In  reptiles  also,  we  find  a  condition  of  the 
muscular  powers  in  perfect  keeping  with  their  feeble  and 
inactive  respiration.  Their  motions  are  slow  and  un- 
frequent,  and  there  is  a  constitutional  sluggishness  and 
indolence.  For  several  months  in  every  year,  they  shut 
themselves  up  in  holes  and  dark  places,  and  remain  in  a 
state  of  torpidity,  in  which  motion  and  sense  are  utterly 
suspended. 

In  fishes,  there  are  relations  between  the  quantity  of 
respiration  and  that  of  muscular  motion,  no  less  uniform 
and  striking.  They  consume  but  little  air,  and  they 
have  but  little  muscular  power. 

Emily. — I  thought  that  they  were  remarkable  in  this 
respect.  Their  motions  are  certainly  very  rapid  ;  and 
salmon  are  said  to  ascend  falls  thirty  feet  high. 

Dr.  B. — True,  indeed,  and  the  darting  of  a  salmon 
or  trout  in  the  water  is  often  compared  to  an  arrow,  but 
such  rapid  motions  cannot  be  continued  longer  than  a 
few  minutes.  Their  powers  are  soon  expended,  and 
not  receiving  a  proportional  supply  from  the  respiratory 
organs,  their  exertions  are  necessarily  short. 

The  relations  between  the  respiratory  function  and 
the  nervous  system,  are  just  as  strict  and  invariable.  In 
cold-blooded  animals,  whose  respiration  is  almost  an 
accessary  circumstance  merely,  the  external  senses  are 
deficient  in  acuteness,  and  the  mental  faculties  are  lim- 
ited and  dull.  The  nervous  system  derives  its  energy 
from  the  blood,  and  it  will  always  be  proportional  to  the 
degree  of  renovation  which  this  fluid  receives  from  the 
action  of  the  respiratory  organs.  In  the  reptiles,  the 
nervous  energy,  weak  as  it  is,  is  sufficient  for  their  pur- 
pose. Strong  sensations,  and  acute  sensibility  were  not 
wanted  by  animals  whose  muscular  power  needs  but  lit- 
tle reanimation,  because  little  is  expended. 


RELATION    OF  DIGESTION    WITH    SENSATION.     239 

In  birds,  the  nervous  system  bears  as  great  a  propor- 
tion to  the  bulk  of  the  body,  compared  with  other  ani- 
mals, as  the  respiratory  organs.  Hence,  the  acuteness 
of  their  sensations  and  their  general  superiority  in  mental 
activity  strongly  contrasts  with  the  sluggishness  of  rep- 
tiles and  the  intellectual  stupidity  of  fishes. 

Digestion  has  also  intimate  relations  with  respiration. 
Emily. — This  is  very  obvious ;  for  one  great  use  of 
respiration  is,  to  separate  those  portions  of  the  food  re- 
ceived into  the  blood,  which  are  unfit  for  the  purposes 
of  ihe  animal  economy,  as  well  as  to  expose  to  the  reno- 
vating influence  of  the  air,  the  really  nutritive  materials, 
It  is  the  office  of  digestion  also,  to  prepare  the  materials 
which  are  to  supply  the  places  of  others  that  are  taken 
away,  and  carried  out  from  the  system  by  means  of  the 
respiratory  organs.  There  must  of  necessity,  therefore, 
be  a  uniform  proportion  of  energy  between  respiration 
and  digestion. 

Dr.  B. — This  is  the  reason  why  birds  possess  suck 
strong  powers  of  digestion,  and  require  food  at  frequent 
intervals.  In  reptiles,  on  the  contrary,  the  digestive 
powers  are  limited,  and  entire  abstinence  is  easily  borne 
for  very  protracted  periods.  In  their  torpid  state,  they 
lie  for  months  without  the  slightest  morsel  of  food. 

Emily. — And  the  reason  is  very  obvious  ;  nothing  is 
carried  away  from  the  system  by  respiration  since  this 
function  is  hardly  perceptible,  and  consequently  nothing 
is  required  from  the  digestive  process. 

Dr.  B. — There  is  a  very  close  relation  between  di- 
gestion, and  sensation  and  motion.  In  the  inferior  ani- 
mals, the  principal  purpose  of  the  latter,  is  to  assist  in 
the  performance  of  the  former ;  both  are  constructed  with 
a  direct  reference  to  the  nature  of  the  food.  The  car- 
nivorous animal  must  not  only  have  a  set  of  digestive 
organs  fitted  to  act  upon  raw  flesh,  but  his  senses  must 
be  sufficiently  acute  to  distinguish  his  prey  at  a  distance  ; 
his  muscular  power  must  be  sufficient  to  enable  him  to 
pursue  and  overcome  it ;  his  claws  must  be  sharp  and 


240  LAWS    OF    COEXISTENCE. 

strong,  in  order  that  he  may  seize  it  and  tear  it  in  pieces  > 
and  his  teeth  must  be  long,  sharp  and  pointed,  for  the 
purpose  of  cutting  and  dividing  it. 

Emily. — And  he  must  also  possess  the  requisite  cour- 
age and  address  to  circumvent  and  attack  his  victim, 
otherwise  all  these  advantages  you  have  mentioned,  will 
be  of  no  avail  to  him. 

Dr.  B. — Certainly  ;  without  these  qualities,  the  lion 
and  tiger  would  never  dare  to  attack  animals  larger  than 
themselves,  and  consequently  could  not  exist. 

Emily. — Without  the  requisite  courage  to  encounter 
the  thick-set  snares  of  the  poultry-yard,  and  the  cunning 
and  subtlety  necessary  to  avoid  them,  Reynard  would 
often  go  to  bed  supperless,  and  dream  of,  instead  of 
feasting  on  chanticleer  and  his  mates. 

Dr.  B. — Herbivorous  animals,  on  the  contrary,  which 
can  digest  only  vegetable  food,  have  velocity  of  the 
muscular  power  instead  of  strength,  whereby  they  avoid 
their  enemies  ;  their  feet  are  destitute  of  claws  ;  their 
teeth  are  blunt  ;  and  their  moral  powers  are  character- 
ised by  timidity  and  distrust. 

The  laws  which  thus  determine  the  relations  between 
the  different  functions,  are  equally  perceptible  in  fixing 
the  relations  between  the  different  parts  of  the  same 
system.  In  the  digestive  system,  for  instance,  the  con- 
struction of  the  jaws,  the  form  of  the  teeth,  the  length, 
convolutions,  and  dilatations  of  the  alimentary  canal,  are 
all  determined  by  one  another,  and  these  relations  are 
so  constant  and  necessary,  that,  like  the  conditions  of  a 
mathematical  problem,  one  being  known,  the  rest  are 
quickly  inferred. 

Emily. — These  laws  of  existence  do  indeed  form  a 
necessary  condition  of  the  existence  of  organic  beings. 
I  never  was  before  aware  that  laws  presided  over  their 
formation,  as  uniformly  as  attraction  and  repulsion  over 
the  operations  of  inorganic  matter.' 

Dr.  B. — Tester id  too  of  feiterino;  the  operations  of  na- 
ture, as  might  perhaps  at  first  sight  seem,  and  prescribing 


LAWS    OF    CO-EXISTENCE.  241 

Jimits  to  its  power,  it  is  but  another  signal <  instance  of 
that  beautiful  harmony  which  pervades  all  its  works,  and 
binds  them  together  as  necessary  parts  of  the  great  gen- 
eral system.  It  has  been  owing  to  an  ignorance  of  these 
beautiful  and  invariable  laws  of  organization,  that  so  many 
impositions  have  been  practised  on  the  community,  and 
even  deceived  rnen  of  good  common  sense,  and  in  other 
matters,  of  general  intelligence.  Those  abominable  mon- 
strosities so  often  exhibited  about  as  veritable  specimens 
of  the  mermaid  race,  are  violations  of  nature  as  gross  and 
absurd  as  the  Centaur  of  the  ancients,  or  the  poetical 
image  which  embellishes  the  Kentucky  hunters'  song, 
"  half  horse,  half  alligator." 

To  recapitulate  these  remarks,  we  observe  generally 
that  the  grand  result  produced  by  the  action  of  the  vital 
organs,  is  not  to  be  considered  merely  as  a  combination 
of  the  action  of  each  particular  organ,  but  as  the  effects 
of  their  necessary  and  mutual  relations  ;  and  consequent- 
ly that  a  change  in  the  condition  of  one  function  will  not 
only  vary  the  general  result,  but  also  the  particular  ac- 
tion of  the  other  functions. 

Emily. — It  seems  in  fact  to  be  very  like  the  economy  of 
our  own  republic,  where  each  portion  of  which  it  is  com- 
posed, not  only  regulates  its  own  concerns,  but  contributes 
its  part  to  the  management  of  the  common  interest. 

.Dr.  B. — Your  comparison  is  as  just  as  it  is  clear. 
Had  a  knowledge  of  these  principles  been  more  gener- 
ally extended,  the  world  would  have  been  spared  those 
absurd  theories,  which  under  the  name  of  philosophy, 
have  been  seriously  constructed  and  greatly  admired. 
One  of  these  philosophers  imagines  that  man  owes  his 
superiority  over  the  animal  creation,  to  the  form  of  his 
hands  ;  another,  to  his  erect  position ;  and  many  others 
to  his  intellectual  gifts,  and  have  proved  the  truth  of 
their  theories,  by  showing  what  a  different  creature  man 
would  be  without  these  several  conditions. 

Emily. — To  talk  about  what  man  would  be,  with  a 
different  conformation  of  this  or  that  organ,  is  about  as 


242  DEATH. 

absurd  as  it  would  be  for  a  geometer  to  speculate  on  the 
probable  state  of  geometry,  if  the  three  angles  of  a  tri- 
angle amounted  to  only  one,  instead  of  two  right  angles. 

Dr.  B. —  Man  is  what  he  is,  not  because  he  possesses 
this  organ  or  that,  but  because  he  is  the  general  result 
or  product  of  a  certain  system  of  organization. 

Such  is  the  history  of  organic  beings ;  it  only  remains 
for  us  now,  to  behold  their  natural  termination  in  death. 
The  animal  functions  first  feel  the  approach  of  the  "  grim 
destroyer,"  and  are  one  after  another  gradually  extin- 
guished before  the  organic  are  sensibly  affected.  The 
muscles  lose  the  power  of  action,  till  the  limbs  and  trunk 
are  motionless.  The  senses  lose  their  acuteness  ;  vis- 
ion grows  dim  and  the  eye-lids  close  ;  the  ear  is  insensi- 
ble to  sound ;  the  voice  is  weak  and  husky.  The  intel- 
lectual faculties  soon  participate  in  the  decay  of  the  sen- 
ses. The  memory  is  obliterated  ;  judgment  errs  ;  and 
the  consciousness  of  the  world  without  fades  from  the 
mind.  Respiration,  circulation,  and  the  other  organic 
functions  still  continue,  till  death  finally  seizes  upon 
them.  Respiration  is  slackened  ;  the  motions  of  the 
heart  are  feeble  and  irregular ;  the  blood  retires  from 
the  vessels  of  the  skin  to  the  central  organs,  where  it  stag- 
nates and  dies.  Thus  proceeding  from  the  circumfer- 
ence to  the  centre,  life  is  gradually  extinguished  through- 
out all  the  system.  The  body  is  now  subjected  to  the 
ordinary  laws  of  matter ;  putrefaction  and  decomposition 
commence ;  and  this  admirable  machine,  which  but  a 
moment  before,  as  it  were,  was  charged  with  youth, 
beauty  and  intelligence,  is  scattered  to  the  elements. 


14  DAY  USE 

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